Demand
Demand and Supply
Why do roses cost more on Valentine’s Day?
Why do TV ads cost more during the Super Bowl ($2.7
sec.) than during Nick at Nite reruns?
Why do hotel rooms in Sun Valley, Idaho cost
more in the winter than in the summer?
Why do surgeons earn more than butchers?
Why do pro basketball players earn more than pro hockey players?
“Econ, Econ”
Why do economics majors earn more than most other majors?
Why are some of you going to major in economics in college?
The answer to these and other economics questions boil down to the
workings of supply and demand – the subject of this chapter.
million for 30
Individual Demand
Market
D
D
+
$2
$3
$2
Demand
“JO”
“Mo”
“Bo”
$3
To
D1 D2
D
+
$3
= $3
$2
$2
[Total]
115
100 115
26 30
39 45
From “individual” demand to “market” demand
And, what if the price of this product decreases from $3 to $2?
A point to point movement on the same “D” curve is a “Change in QD”
35 40
And – what if this good prevents cancer, so we have an increase in “D” for it.
Consumers “willingness to buy”
Price decreases; QD increases
P QD
$5
4
3
2
1
10
20
35
55
80
$5
D
$4
$3
$2
$1
0 10 20
35
55
80
Quantity Demanded
…a specified time period
…other things being equal
QD – how much will be purchased at a specific price [& date].
D
iPhone
$399.00
[with 2 yr contract]
[8GB]
Reasons For Downsloping “D” Curve
1. Income Effect –current buyers buy more.
2. Substitution Effect– new buyers now purchase.
3. Diminishing Marginal Utility - because buyers
of successive units receive less marginal utility,
they will buy more only when the price is lowered.
Change in QD
1. Price change
2. Movement
Price
QD
$250.00
[up/down the demand curve]
3. Point to point [along the curve]
Inverse
relationship
QD2 curve”. [“all prices”]
“D” refers toQD
the1“whole
“QD” refers to a “point on the curve”
based on a “particular price.”
D
1. Income Effect
•
•
When things are expensive, money buys less
When things are cheap, money buys more
P1
P2
QD1 QD1
2. Substitution Effect
•
When apples are expensive and their
substitutes (pears) are relatively cheap,
I buy fewer apples and more pears
3. Diminishing Marginal Utility
•
•
Each additional unit of an item purchased gives less marginal utility
(happy points) than the previous unit. Therefore, the only way I will buy
more is if the price is lower.
Ex. When I’m hungry, I typically will buy 2 breakfast tacos. The
reason I don’t buy a third taco is because the marginal utility of the
third taco is less than the price of the taco. But, if the price of the taco
is less than the marginal utility of the taco, then I will buy the third taco
Picture of
Law of
Demand
Elastic
or
Inelastic
(Total Receipts Test)
$2
$1
Elastic
Inelastic
20
30
Total Receipts Test
20 x $2 = $40.00
30 x $1 = $30.00
40
50
Total Receipts Test
20 x $2 = $40
50 x $1 = $50
11. Elasticity of D – the way price affects QD.
12. Elastic - QD that is very responsive to price.
13. Inelastic - a chg in price has little impact on QD.
Elastic (flexible) Demand
1. Substitutes (butter)
2. Luxury (mink coat)
3. Expensive (car)
4. Has durability (refrigerator)
5. Lasts a long time (gas-guzzling car)
Inelastic (inflexible) Demand
1. No substitutes (milk)
2. Necessity (insulin)
3. Inexpensive (safety pin)
4. No durability (pencil)
5. Lasts only a short time (bread)
Elastic Demand For Cassette Tapes
“TR” Test
$2.50x100,000=$250,000
$1.50x600,000=$900,000
+$650,000
D
-$1
.
Think of “responsiveness” as “flatness”.
D
“TR” Test
$2 = $30 bil.
$1 = $20 bil.
-$10 bil.
-$1
+25% QD
Change in
“Demand”
[curve]
[“TIMER”]
Consumers change
their minds at each
and every price.
Based on good or bad
publicity about OJ.
.
16 oz. Orange juice = 220 calories
16 oz. Tomato juice = 78 calories
Quantity Demanded
vs. Demand
Quantity Demanded [QD] is triggered by a price chg.
The quantities of a good or service that people will
purchase at a specific price at a given time.
Demand [D] is triggered by “TIMER” [non-price].
A schedule of the total quantities of a good or service
that purchasers will buy at different prices at a
given time.
Demand is a bunch of QD’s strung together.
“Demand Shifters” [TIMER]
1.
2.
3.
4.
Taste [direct]
Income [normal-direct] [inferior-inverse]
Market Size [number of consumers-direct]
Expectations [of consumers about future *price-direct,
about future availability-inverse, or about future income–direct.
5. Related Good *Prices [substitutes-direct] [complements-inverse]
D1 D2
D3 D1 D2
P
Butter
D1
D2
P
P2
Complement
[inverse]
P
P1
D
QD1 QD2
Bread
Substitute
[Direct]
Bagels
Change in “D” [curve]
1. Non price change [“TIMER”]
2. Whole “D” curve shifts
QD3 QD1 QD2
[There is a change in “QD” but it is
not caused by a change in “price.”
[QD-”single price”; D-”all prices”]
D1 D2
P
D3
QD3 QD1 QD2
Bell Bottoms
Mini
Hip Huggers
Skirts Platforms
1. An “Increase in Taste” shifts the D curve right
a. The Nehru jacket came & went in 6 months.
b. Jordache jean demand created by TV
c. Leisure suits and bell bottoms.
d. Technological change may cause
consumer taste to change[slide rules].
Increase in demand for dark chocolate after studies
revealed that there were health benefits from eating it.
Scientists have discovered that smokers who ate dark chocolate had
less hardening of the arteries and a lowered risk of blood clots.
D1
P
D2
Advertising Can Shift “D” [& also impact QD]
D1
D2
$45
QD1
QD2
D1 D2
Steak
More income
results in
more demand
for steak;
less demand
for spam.
P
QD1 QD2
Spam
Less income
results in
more demand
for spam;
less demand
for steak.
2. Change in Income
Normal Good – goods whose demand
varies directly with income.
Inferior Good – goods whose demand
varies inversely with income.
Butter, filet, steel-belts, new clothing & new cars
v.
Margarine, spam, used tires, old clothing & old cars
Income
Demand
For
Spam
Demand
For
Steak
D1 D2
P
More demand
for both spam
and steak.
QD1 QD2
can increase/decrease from
economic decisions, advertising, and
government political decisions (China).
Ex: The large “baby boom” of 1946-64
increased the demand for baby supplies.
An increase in life expectancy increased
demand for for medical care, retirement
communities, and nursing homes.
Increase in # of consumers
If the iPod-Touch is expected to
increase in price from $299 to $399.
D1 D2
iPod-Touch
P
QD1 QD2
car
Consumer expectations about future product
price, future availability, & future income.
Ex: When the Korean War broke out in the
summer of 1950, new car sales boomed (also
washers and refrigerators) out of the
expectation of a production stoppage like
during WWII. None occurred but it was the
expectation that affected new car demand.
D1 D 2
P
Complement
[Inverse]
Gangsta Grills
D
D1
P1
D2
P
P2
QD1 QD2
Chrysler 300s
MV X PQ
Substitute
[Direct]
Toyotas
There are three types of goods.
1. Independent goods – price change
of one has no impact on the other.
Ex: fishhooks & pantyhose or salt & shoelaces
2. Substitute goods(“competing goods”)
- price change of one affects the
demand of the other directly.
Ex:
7Up & Coke or Miller & Bud
D1
D2
QD2 QD1
3. Complementary goods(“go together”)
- price change of one affects the
demand for the other inversely.
Peanut butter & jelly
D1 D2
Camera
QD1 QD2
Film
Cereal & milk Coffee & donuts
[Increase in price of one; increase in “D” of the other]
D1 D2
D
P
P2
QD
QD
P1
QD2
Price
Of
7UP
QD1
Demand
for
Dr Pepper
[Decrease in price of one; increase in the “D” for the other]
P1
P2
D 1 D2
QD1 QD2
Car Prices
P
QD
QD
Gasoline Demand
No change
in price
I’m making more
money without
dropping my prices.
They are so cheap that
even dogs are buying cars
Substitutes – Direct
[Increase in price of one; increase in “D” of the other]
D
P
P2
D1
D2
QD
QD
P1
QD2
QD1
Demand for
Microsoft’s Zune
Price of
iPod Video
1977, Bill was
arrested for
running a stop
sign and driving
without a license.
Substitutes - Direct
D1
Price
Of
Chicken
D2
Demand
for
Turkey
Although both monitor & laptop QDs changed, it is still
a “Change in D” for those two, because the QD changes
were not triggered by a change in price.
The price of desktop computers did change so there is a
“Change in QD” for desktop computers.
D1 D 2
P
Complement
[inverse]
Monitor
D
P1
P2
QD1 QD2
Desktop
Computers
D1
D2
P
Substitute
[Direct]
Laptops
Substitutes - Direct
D1
Price Of
Windows
Computers
D2
Demand
for
Apple
Computers
Substitute/Complement Relationships
D
D1
“Substitutes”
P1
Price
Price
P2
P
D2
Decreases Decreases
QD2 QD1
QD1 QD2
Hot Dogs [DIRECT] Hamburgers
.
D
P1
“Complements”
Demand
Price
Decreases Increases P
D1
D2
P2
QD1 QD2
Pancakes
[inverse]
QD1
QD2
Syrup
“TIMER”
P
Tastes [direct]
Incomes
-Normal [direct] & Inferior[inverse]
Market Size(# of consumers) [direct]
Expectations of consumers about
[future price-direct; future
income [direct]; and availability [inverse]
Related Good Price Changes
[substitutes-direct; complements-inverse]
Helmets
Increase in “QD”
Decrease in “QD”
[caused by a “decrease in price”]
[caused by an “increase in price”]
D
D
1. Price change
2. Movement
3. Point to point
P1
P2
[“Snap
shot of 1 pt in time]
P2
P1
QD2 QD1
QD1 QD2
D1 D2
P
Change in “D” [“TIMER”]
1. Non-price
2. Whole curve
3. Shift
D1
P
D2
[“Time passes”]
“Increase in D”
What could cause an “increase in Demand?”
1. Increase in taste
2 .Increase in income [normal good]
3. Decrease in income [inferior good]
4. Increase in market size [# of consumers]
“Decrease in D”
5. Expectations of a shortage
6. Expectations of a price increase
7. Expectations of positive future income
8. Incr in price of a substitute for product “X”
9. Decr in price of a complement of product “X”
Change in QD
[price change/movement/pt to pt]
Change in D [curve]
[non-price change/shift/whole curve]
5 Demand Shifters [“TIMER”]
1. Taste [direct]
2. Income [normal - direct] [inferior - inverse]
3. Market Size [number of consumers - direct]
4. Expectations [price, income, & availability]
5. Related Good Price changes
[substitutes - direct] [complements - inverse]
D 3 D 1 D2
D
P1
P2
QD3 QD1 QD2
QD1 QD2
[“Moving” along the crab demand
because of a crab price change]
curve”
“Shifting the crab demand curve”
+/- QD/D
+ QD
___
___ 1. Crab sales are affected by a drop in crab prices.
D 2. An increase in income causes the demand curve for crab to shift.
___
+ ___
+/- D/QD
Graph The Black Boldfaced Items
D 1. A population increase affects sales of Pepsi Colas.
+ ___
___
- ___
___
D 2. Consumer incomes in the city of Plano decrease,
with the result that jewelry sales are affected.
+ QD
___
___ 3. A camera store has a sale that features 25% off the price of all cameras.
- QD
___
___ 4. Texas imposes a 15% luxury tax on the sale of sailboats.
___
+ ___
D 5. A frost in Florida destroys 60% of the orange crop and increases
expectations about a future price increase of oranges.
- ___
___
D 6. Consumers expect the prices of digital cameras to decrease next month.
- ___
___
D 7. The sale of DVDs is affected by a 20% increase in the price of DVD players.
D
P2
DVD
Players
D1
[Complements -
P1
INVERSE]
DVDs
+
D 8. The sale of buns is affected by a 20% decrease in the price of
___ ___
QD2 QD1
hamburger meat.
Hamburger
meat
D1
D
[Complements -
P1
INVERSE]
P2
Buns
+ ___
D 9. The sale of Kangaroo meat in Europe [Roo Steak] is affected
___
by a 25% increase in the price of beef.
QD1 QD2
P2
P1
D
D1
Beef
Kangaroo meat
[Substitutes -
DIRECT]
+
___QD
___ 10. Dunkin Donuts lowers the price of donuts & experiences a change in sales.
QD2
QD1
D
P1
P2
D
QD1 QD2
[INVERSE]
Change in QD
Price Change
Point to Point
Movement
What is not held constant
in these two graphs? Price
P2
P1
QD2
QD1
“Change in Demand”
D1
D1 D2
P
P
Q1 Q2
Do not confuse these
two with “Chg in QD”
Change in Demand
Non-Price Change
Whole Curve
Shift
D2
Q2 Q1
[D – “TIMER; QD – price change [inverse]
MP3 Player Phone
[stereo sound, downloadable
sound games and ring tones]
A
__1.
Which will cause an “Increase in D”
for
MP3 Player phones?
a. increase in income
c. increase in the price of MP3 Player phones
b. decrease in income
d. decrease in the price of MP3 Player phones
___2.
Which will cause an “Increase in QD” for MP3 Player phones?
C
a. decrease in income
c. decrease in the price of MP3 Player phones
b. increase in income
d. increase in the price of MP3 Player phones
___3.
Which will cause a “Decrease in D” for Projectors?
C
a. increase in the price of projectors
c. decrease in # of consumers
b. decrease in the price of projectors
d. increase in projector taste
A
___4.
Which will cause a “Decrease in QD” for Projectors?
a. increase in the price of projectors
c. decrease in # of consumers
b. decrease in the price of projectorsd. increase in projector taste
QD & D Practice Quiz[Snickers]
1. What would cause an “increase in QD” for Snickers?
a. increase in price of Snickers b. decrease in price of Snickers
c. decrease in income
d. increase in number of consumers
2. What would cause an “increase in D” for Snickers?
a. increase in taste
c. decrease in income
b. decrease in price of Snickers
d. increase in the price of Snickers
3. What would cause a “decrease in QD” for Snickers?
a. increase in taste b. decrease in price of Snickers c. increase in price of Snickers
4. What would cause a “decrease in D” for Snickers?
a. decrease in income b. increase in taste c. decrease in price of Snickers
5. An “increase in the price of Butterfingers would
cause a(n) (increase/decrease) in (QD/D) for Snickers?
NS 1-10
1. (Demand/Supply) is identified as quantities consumers are willing
and able to buy at various prices during a given time period.
2. The law of demand says that price & QD are (directly/inversely) related.
3. The most important variable influencing decisions to produce and
purchase goods is (technique/price). (Price/income) is not held
constant when moving along a stable demand curve.
4. Income effect-the increase or decrease in purchasing power
brought on by a change in (taste/market size/price).
5. Substitution effect – tendency to substitute a (higher/lower)
-priced product for a more expensive product.
6. Diminishing marginal utility – utility, or (determination/anger/satisfation)
decreases as more of the same product [Snickers] is consumed.
7. The law of demand refers to a (movement/shift) along a demand curve.
8. Substituting chicken as the price of steak goes up is an example
of the (income/substitution) effect.
9. When the price of caviar falls, the purchasing power of our money income
rises & thus permits us to purchase more caviar. This is the (income/substitution) effect.
10. The demand (curve/schedule) is a numerical tabulation showing QD at each price.
The demand (curve/schedule) is a graphical representation of the law of demand.
NS 11 - 20
11. Elasticity of demand–the way price affects (attitude/quantity/market size).
12. (Inelastic/Elastic) demand – demand that is very responsive to price.
[A small price increase causes a large decrease in quantity demanded.]
13. (Inelastic/Elastic) demand-when a change in price has little impact on QD.
14. The 3-item test for elastic demand are substitutes, luxury items,
15.
16.
17.
18.
19.
and (inexpensive/expensive) items.
The 3-item test for inelastic demand are no substitutes,
necessities, and (inexpensive/expensive) items.
Expensive cars have (inelastic/elastic) demand.
Pepsi Cola has (inelastic/elastic) demand.
Insulin has (inelastic/elastic) demand.
The elastic demand curve is more (horizontal/vertical). [much change]
20. The inelastic demand curve is more (horizontal/vertical). [not much change]
NS 21-26
21. With the invention of the calculator, the demand curve for the
slide rule (increased/decreased).
22. When Forest Gump went to China & the U.S. followed by
opening up relations with China, the demand curve for
Coke (increased/decreased).
23. An increase in income would (increase/decrease) the demand
for used clothing. [inferior good]
24. A decrease in income would (increase/decrease) the demand
for lobster. [normal good]
25. A decrease in the price of product X [lumber] will (incr/decr)
the demand for the complementary product Y. [nails]
26. After Brooke Shields[15] did her national TV ads[“Nothing comes
between me and my Calvin’s”], the “D” curve moved (right/left).
$45
NS 27-38
27. An increase in the price of Pepsi causes the
demand curve for Coke to move to the (right/left).
28. If there is a sale on shirts, the demand curve for ties will move
to the (right/left).
29. If a man’s workplace is about to close down, his demand
curve for major purchases would move to the (right/left).
30. If a cure for lung cancer were found, the demand curve for
cigarettes would move to the (right/left).
31. If the price of pancakes decreases, the demand
for syrup, a complement, will (increase/decrease).
32. If the price of butter decreases, the demand for margarine will (incr/decr).
33. A “change in QD” is caused by (price change/TIMER) [a “movement”]
34. A “change in D” is caused by (price change/TIMER) [a “shift”]
e
“Econ, Econ”. Let
tell you about econ.
The End
1. Madonna gave a concert at the AAC after doubling the ticket
price and experiencing a change in anticipated attendance.
2. A decrease in taste causes the demand for lobster to shift.
3. A 20% increase in the price of Pepsi affect the sale of Coke.
4. Consumers expect the price of cell phones to increase 25% next month.
5. The sale of Ford F150s is affected when the U.S. begins trading with Cuba.
6. New autos decrease in price by 20% & the sale of gasoline is affected.
7. Victoria’s Secret increases the price of its thongs by
40% and experiences a change in the volume of sales.
8. Britney Spears triples the price of her album,
“Oops, I flunked Econ Again,” and sales are affected.
9. A drought in Texas destroys 40% of the state’s peaches & increases
consumer expectations about a future price increase of peaches.
10. A 15% decrease in the price of motorcycles affect the sale of helmets.
Taste [direct]
Income [normal-direct] [inferior-inverse]
Market Size [# of consumers-direct]
Expectations [price-direct] [income-direct] [availability-inverse]
Related Good
Price Changes8.–QD
[subs-direct] [complements-inverse]
6.+D
7.–QD
9.+D 10.+D
1.–QD
2. –D
3. +D
4.+D
5.+D
1. Christina gave a concert at the AAC after lowering the ticket
price and experiencing a change in anticipated attendance.
2. An increase in taste causes the demand curve for lobster to shift.
3. The sale of coke is affected by a 20% decrease in the price of Pepsi.
4. Consumers expect the price of XBOX to decrease 25% next month.
5. The sale of Dr Pepper is affected when the U.S. goes to war with China.
6. New SUVs decrease in price by 30% & the sale of gasoline is affected.
7. Victoria’s Secret decreases the price of its teddies by
50% and experiences a change in the volume of sales.
8. The Spice Girls lower the price of their album, “Oops,
We Actually Passed Econ,” and sales are affected.
9. A freeze in California destroys 70% of the state’s oranges and increases
consumer expectations about a future price increase of oranges.
10. A 50% increase in the price of bread affect the sale of bagels.
Taste [direct]
Income [normal-direct] [inferior-inverse]
Market Size2.+D
[# of consumers-direct]
1.+QD
3. -D
4.-D
5. -D
Expectations [price-direct] [income-direct] [availability-inverse]
6.+D
7.+QD
8.+QD [complements-inverse]
9.+D 10.+D
Related Good
Price Changes[subs-direct]
Review of Demand
D
iPhone
$399.00
[with 2 yr contract]
[8GB]
Reasons For Downsloping “D” Curve
1. Income Effect –current buyers buy more.
2. Substitution Effect– new buyers now purchase.
3. Diminishing Marginal Utility - because buyers
of successive units receive less marginal utility,
they will buy more only when the price is lowered.
Change in QD
1. Price change
2. Movement
Price
QD
$250.00
[up/down the demand curve]
3. Point to point [along the curve]
Inverse
relationship
QD2 curve”. [“all prices”]
“D” refers toQD
the1“whole
“QD” refers to a “point on the curve”
based on a “particular price.”
“Demand Shifters” [“TIMER”]
1.
2.
3.
4.
Taste [direct]
Income [normal-direct] [inferior-inverse]
Market Size [number of consumers-direct]
Expectations [of consumers about future price-direct,
about future availability-inverse, or about future income–direct.
5. Related Good Prices [substitutes-direct] [complements-inverse]
D3
D
1
D3
D1 D2
P
Games
for PS3
D1
D2
P
P2
Complement
[inverse]
P
P1
D
QD1 QD2
PS3
Substitute
[Direct]
XBOX
Changes in “D” [curve]
1. Non price change [“TIMER”]
2. Whole “D” curve shifts
QD3 QD1 QD2
[There is a change in “QD” but it is
not caused by a change in “price.”
[QD-“singe price”; D-”all prices”]
A decrease in taste
for videos results in a
decrease in demand.
D1 D2
An increase in taste
for DVDs results in an
increase in demand.
D3
P
QD3 QD1 QD2
New Cars
D1
More income
results in
more demandP
for new cars;
less demand
for used cars.
D2
Used Cars
QD1 QD2
Less income
results in
more demand
for used cars;
less demand
for new cars.
This is what we told one billion Chinese, as new potential
consumers, when we opened trade relations with them in 1972.
D1 D2
P
New Cars
More demand
for both normal
& inferior goods
QD1 QD2
Used Cars
$399
If Steve Jobs responds to iRate customers who
bought the iPhone at $599 and says, “iSorry,
we will raise the price back to $599 in 3 weeks.”
D1 D2
Buy it now to save money.
iPhone
P
QD1 QD2
Let’s say that we are coming out of recession & consumers
feel secure about their jobs. [Positive future income]
D1 D2
P
QD1 QD2
Let’s say that we are going into a recession and consumers
don’t feel secure about their jobs. [Negative future income]
D1
D2
P
QD2QD1
D1 D 2
D
D1
P1
P
D2
P
P2
Complement
[Inverse]
Milk
QD1 QD2
Cereal
Substitute
[Direct]
Pop Tarts
D
Coke
P1
D1 Dr Pepper
D2
P2
D
Substitutes - Direct
Motorcycles
D1
D2
P1
P2
QD1 QD2
Helmets
D
P1
P2
D
QD1 QD2
[INVERSE]
Change in QD
Price Change
Point to Point
Movement
What is not held constant
in these two graphs? Price
P2
P1
QD2
QD1
“Change in Demand”
D1
D1 D2
P
P
Q1 Q2
Do not confuse these
two with “Chg in QD”
Change in Demand
Non-Price Change
Whole Curve
Shift
D2
Q2 Q1
[D – “TIMER; QD – price change [inverse]
[Revised from previous]
__1.
Which
B
of the following will cause an “Decrease in D” for
iPod nanos?
a. increase in income
c. increase in the price of iPod nanos
b. decrease in income
d. decrease in the price of iPod nanos
D
___2.
Which will cause an “Decrease in QD” for iPod nanos?
a. decrease in income
c. decrease in the price of iPod nanos
b. increase in income
d. increase in the price of iPod nanos
D
___3.
Which of the following will cause a “Increase in D” for HDTVs?
a. increase in the price of HDTVs
c. decrease in # of consumers
b. decrease in the price of HDTVs
d. increase in HDTV taste
B
___4.
Which of the following will cause a “Increase in QD” for HDTVs?
a. increase in the price of HDTVs
b. decrease in the price of HDTVs
c. decrease in # of consumers
d. increase in IPOD taste
QD & D Practice Quiz
[“Revised”]
1. What would cause a “decrease in QD” for KitKats?
a. increase in price of KitKats
c. decrease in income
b. decrease in price of KitKats
d. increase in number of consumers
a. increase in taste
c. decrease in income
b. decrease in price of Kitkats
d. increase in the price of KitKats
2. What would cause a “decrease in D” for KitKats?
3. What would cause an “increase in QD” for KitKats?
a. increase in taste b. decrease in price of KitKats c. increase in price of KitKats
4. What would cause an “increase in D” for KitKats?
a. increase in # of consumers b. decrease in taste b. decrease in price of KitKats
5. A “decrease in the price of Reese’s would
cause a(n) (increase/decrease) in (QD/D) for KitKats?
Elastic/Inelastic Demand
.
Go over Total
Receipts Test
For Elastic &
Inelastic