ps#1 answers

Econ 301 – F07
ANSWERS to PROBLEM SET 1 - due in class on Tuesday September 11
1. Argentina and Brazil both produce leather and coffee with labor. The labor input is measured in
hours, coffee is measured in gallons and leather is measured in yards. The table below shows labor
requirements to produce a unit of coffee and of leather in each country. (It is assumed that the labor
requirements per unit of output in production remain the same irrespective of the quantity of the two
goods produced.) Each country has 120 hours of labor available, which can be allocated between the
two activities. Labor can not go from one country to the other but coffee and leather can.
1 gallon of
1 yard of leather
10 hrs
15 hrs
4 hrs
20 hrs
a. Graph the production possibilities frontier (PPF) for both Argentina and Brazil (separately)
clearly labeling the axes. (Note: The labor requirements per unit of output remain constant
irrespective of the quantity produced.)
[ANSWER] LArgentina = LBrazil = 120 hours
Argentina's PPF
Leather (yards)
Brazil's PPF
Leather (yards)
Coffee (gallons)
Coffee (gallons)
b. What is the opportunity cost of producing an extra gallon of coffee in Argentina? In Brazil?
[ANSWER] The opportunity cost of producing an extra gallon of coffee = the marginal opportunity
cost of producing coffee in terms of leather (MOC)
Argentina: MOC of Coffee is 2/3 (yards of leather/1 gallon of coffee)
Brazil: MOC of Coffee is 1/5 (yards of leather/1 gallon of coffee)
c. What is the opportunity cost of producing an extra yard of leather in Argentina? In Brazil?
[ANSWER] Argentina: MOC of Leather is 3/2 (gallons of coffee/1 yard of leather)
Brazil: MOC of Leather is 5 (gallons of coffee/1 yard of leather)
d. Suppose that both Argentina and Brazil are self sufficient i.e., they each rely on their own
production for their consumption and do not trade with each other. Also assume that each nation
devotes exactly a half of its total labor availability to the production of coffee and the rest to the
production of leather. Indicate the combination of coffee and leather produced and consumed in
each country on the graphs of part (a).
[ANSWER] see the graph in (a).
Argentina devotes 60 hours of its labor in producing coffee and 60 hours of its labor in producing
leather. 10 hours are used to produce 1 gallon of coffee. 60/10 = 6 gallons of coffee is consumed in
Argentina, and 60/15 = 4 yards of leather. The combination of coffee and leather produced and
consumed in Argentina is (Coffee, Leather) = (6 gallons,4 yards). Brazil produces 15 gallons of
coffee with 60 hours of its labor and 3 yards of leather with 60 hours of its labor. The combination
for Brazil is (Coffee, Leather) = (15 gallons, 3 yards).
e. Suppose each country devotes all its labor availability to the production of the commodity in
which it has a comparative advantage (i.e., a relatively lower opportunity cost). Indicate the
production point of each country after specialization. Again use graphs for part (a).
[ANSWER] see the graph in (a).
Argentina specializes in producing leather. All 120 hours are used to produce leather and the
production point of Argentina is (Coffee, Leather) = (0 gallon, 8 yards).
Brazil specializes in producing coffee. All 120 hours are used to produce coffee and the production
point of Brazil is (Coffee, Leather) = (30 gallons, 0 yard).
f. Show that the two countries could now exchange coffee for leather so that the consumption point
of both countries (after specialization and exchange) lies outside of their own PPFs. Give a
specific example.
[ANSWER] see the graph in (a).
For example, Argentina produces 8 yards of leather. Brazil produces 30 gallons of coffee. They
agree to an exchange where Argentina gives Brazil 3.5 yards of leather in exchange for 8 gallons of
coffee. So Argentina would consume 4.5 yards of leather and 8 gallons of coffee and Brazil would
consume 3.5 yards of leather and 22 gallons of coffee. Note that both countries are consuming
MORE of both coffee and leather as compared to their consumption point in part (d) and that both
countries are consuming bundles that are outside their individual PPFs. That is to say, if Argentina
made 8 gallons of coffee for itself, it could only have 2.67 yards of leather. And if Brazil made 22
gallons of coffee for itself it could only have 1.6 yards of leather.
g. Suppose we add Uruguay to the picture with 60 hours of labor and with an input requirement of
5 hours of labor for each unit of coffee and 5 hours of labor for each unit of leather. How would
this alter the joint PPF assuming we look at all three countries?
Argentina (A)
Brazil (B)
Uruguay (U)
1 gallon of coffee
10 hrs
4 hrs
5 hrs
1 yard of leather
15 hrs
20 hrs
5 hrs
MOC of coffee
2/3 yards
1 yard
1/5 yards
(the middle)
(the smallest)
(the largest)
MOC of leather
3/2 gallons
5 gallons
1 gallon
(the middle)
(the largest)
(the smallest)
12 gallons in coffee, or
30 gallons in coffee, or 6
12 gallons in coffee, or
Production Rates
8 yards in leather
yards in leather
12 yards in leather
NOTE: MOC represents the marginal opportunity cost.
- Now see graph…
The Joint PPF
U and A specialize in leather production,
B varies.
Leather (yards)
U specializes in leather production,
B specialize in coffee production,
and A varies.
A specializes in leather production,
B varies.
B specializes in coffee
production, A varies.
A and B specialize in coffee production,
U varies.
Coffee (gallons)
The joint PPF expands.
h. Assuming a market with only these three countries as suppliers of coffee, construct the coffee
supply curve based on the principle of comparative advantage.
Quantity of Coffee
Relative Price of Coffee
0 gallons
0 yards
30 gallons
1/5 yards
42 gallons
2/3 yards
54 gallons
1 yard
Who is Producing Coffee
No country
Brazil, Argentina
Brazil, Argentina, Uruguay
Supply Curve for Coffee
Relative Price yards)
Brazil, Argentina, Uruguay
Brazil, Argentina
Coffee (gallons)
2. Consider the following two equations that describe market activities in the Cortland NY tire market.
Let X = number of tires per month and P = price per tire
Equation A: X=500-2P
Equation B: X=-25+P
a. Which equation would represent the demand curve and why?
[ANSWER] Equation A would represent the demand curve. The slope of the price, -2, is negative.
It describes that the quantity demanded of tires (XD) decreases when the price (P) increases.
b. Which equation would represent the supply curve and why?
[ANSWER] Equation B would represent the supply curve. The slope of the price, 1, is positive. It
describes that the quantity supplied of tires (XS) increases when the price (P) increases.
c. Find the market equilibrium price and number of tires traded, i.e., P* and X*.
[ANSWER] At the market equilibrium, XD=XS, 500-2P = -25+P. => 525=3P => P* = 175 and
d. Graph the equilibrium and label your graph carefully.
[ANSWER] Demand Curve: X=500-2P / Supply Curve: X=-25+P
P (per tire)
0 Xquota=75 X*=150 187.5
X (number of tires per month)
e. Suppose there was a quota placed on this market. What set of values for the quota would make
the quota binding?
[ANSWER] The quantity quota, Xquota, must be below X* to be binding. Thus, any Xquota in the
range of (0,150) would make the quota binding.
f. Suppose the quota is set at Xquota= 75. Carefully and completely describe the consequence of
this quota on both demanders and suppliers. Show its effect in your diagram.
[ANSWER] Sellers would produce Xquota=75 with the price, P0=100, but could sell tires with the
price, P1=212.5 since the demand for tires would be willing to pay up to the price, P1=212.50 with
Xquota=75. The supply is really the original supply curve up to X=75 and then supply becomes
vertical at X=75. Thus, the new equilibrium price is higher than P*=175. See the graph in (d)
g. Suppose Ima Smart insists that a better policy is to impose a price floor that is set equal to the
market price you would get with the quota. Analyze Ima's suggestion using your graph and the
demand and supply equations.
[ANSWER] Suppose that the price floor imposed is P1=212.50. At P1=212.50, sellers want to sell
187.5 (XS=-25+P1=-25+212.50=187.5), but buyers only want to buy 75 (XD=500-2P1=5002*212.50=75). There is a surplus of 112.50=187.5 - 75. See the graph in (d).
h. Suppose that INSTEAD OF THE QUOTA the mayor of Cortland decides to place a per unit tax
of $5.00 per tire on each tire sold. The mayor decides to collect the tax revenue from the
suppliers of tires. Determine the new market situation and figure out how much demanders now
pay and how much suppliers now receive per tire after all is said and done (that is after all tire
taxes are paid). What side of the market would you say seems to have “eaten” relatively more of
the tax and why?
[ANSWER] The tax will be collected from the suppliers. After the tax, the suppliers’ “market”
supply curve is PS=30+X (note it’s best to add the $5 tax directly to the INVERSE supply curve). At
the new equilibrium, newPS=oldPD, 30+X* = 250 – 1/2X* => 1.5X* = 220  newX*=146.67 and
newPD=176.67. So the demanders pay 176.67 per a tire and the suppliers receive 171.67 (which is
176.67 minus the tax of 5) per tire. Note that suppliers have the relatively higher economic price
incidence. That is to say they “eat” 175-171.67 = $3.33 of the tax while demanders only “eat”
176.67-175 = $1.67 of the tax.
3. Consider a particular service - your choice. Listed below are some events that could have some
effect on one or more of the following with respect to that service: quantity demanded, quantity
supplied, demand, and supply. Indicate which of the above four are directly affected and in what
direction (i.e., increase, decrease, etc.).
Let’s consider the education service of private schools.
a. The service becomes more fashionable.
[ANSWER] There is an increase in demand for the education service. The demand curve shifts
b. An income tax is levied on consumers.
[ANSWER] Income decreases as an income tax is imposed. Assuming the good is normal, which is
probably is in this case, a decrease in income decreases the demand for the education service. The
demand curve shifts left.
c. There is a rise in the price of an essential input used in production of the service.
[ANSWER] The rise in the cost of providing the education service decreases supply. The supply
curve shifts left.
d. The price of the service itself changes.
[ANSWER] An increase in the price of the education service decreases the quantity demanded, and
increases the quantity supplied. A decrease in the price of the education service increases the
quantity demanded, and decreases the quantity supplied.
e. The price of a close substitute (substitute in consumption) increases.
[ANSWER] Suppose that the price of the education services of public schools increases. Since
private education and public education are substitutes in consumption, demand for private education
will increase, i.e., shift to the right.
4. Before market reforms were initiated in the Soviet Union back in 1991, prices were often set by the
a. Explain, with the aid of a graph, why there were lines for ordinary consumer goods, such as
[ANSWER] At the market equilibrium, the equilibrium price is P* and the equilibrium quantity
demanded and supplied is X*. But when the government set the price as P0 < P*, there is a market
shortage, X0D-X0S. The quantity demanded is higher than the quantity supplied.
b. In October, 1990, the Soviet government announced that soap prices would double as of January
1, 1991. In the days just following the announcement soap lines increased. Explain how this
could have happened.
[ANSWER] In October, 1990, the price of soap is P0. When the government announced, people
knew that the price of soap would double after 3 months, January 1, 1991. People would be willing
to buy more than the amount that they needed with cheaper price. Thus, the demand for soap
increased in 1990 if they expect prices to really increase sharply in 1991.
5. Suppose the supply function of apples in Upstate New York is: XS = 20 + 2PX – 3Y + 4Z where X
refers to apples. If the supply for apples also depends on fertilizer, which variable to do you think is
the price of fertilizer, Y or Z? Why do you think so?
[ANSWER] Y would be the price of fertilizer. Fertilizer is an input to produce apples. The coefficient
of Y, -3, in the supply function is negative. It implies that when the price of fertilizer increases, the
suppliers would want to produce fewer apples.
6. Suppose that the demand for pork is QD = 286 – 20P where P is the price of pork. Suppose that the
supply for pork is: QS = 178 + 40P – 60Ph where P is the price of pork and Ph is the price of hogs.
Mathematically, how does the equilibrium price of pork vary as the price of hogs changes if the
variables that affect pork demand are held constant at their “ceteris paribus” values?
[ANSWER] At equilibrium, QD=QS
Then, P*=1.8+Ph
From the equation above, the equilibrium price of pork (P*) has a positive relation to the price of hogs
(Ph) and in fact the derivate of P* with respect to Ph = 1, so for every incremental change in the price of
hogs there is an equal incremental change in the eq. price of pork.
7. Use a demand and supply diagram to explain the statement, “Talk is cheap because supply exceeds
demand.” At what price is this comparison being made?
[ANSWER] Let’s consider the market for Talk. The graph shows that “talk is cheap,” i.e. its market
price is zero and that at this price, quantity supplied exceeds quantity demanded. Note that this is not
the ONLY correct answer, you might have some similar answer that makes essentially the same point.