DECISIONS, DECISIONS, DECISIONS
Name:
A friend has asked you to help her decide which of three cellular phone package
is best for her. The cost of purchasing the phone is the same in all cases.
Details of the three plans are given below:
Plan #1 - Rover charges $12 per month, plus $0.15 per minute,
Plan #2 - Crystal Net charges a flat fee of $27 for up to 200 minutes per month, and
Plan #3 - Ring Mobility charges $15 per month, plus $0.10 per minute.
1. Select the equation that represents the total cost of each of the three cellular phone
packages. There are more equations than you need (select three – one per plan)
If “Y” represents the total cost and “x” represents the number of minutes.
Y = 0.15x + 10
Y = 27
Y = 0.12x + 15
Y = 0.10x + 15
Note: there are two extra equations
Name of Cellular Package
Equation y =
Y=
Rover
Crystal Net
Y=
Ring Mobility
Y=
Y = 0.15x + 12
2. Get your calculator ready…
Press the buttons 2nd +
Press 2nd Y=
Set up your window…hit the WINDOW button
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DECISIONS, DECISIONS, DECISIONS
3. Use your calculator to graph each relation. Use the equations from question #1.
Graph the equations in Y1, Y2, and Y3 (do them one at a time) and label each of the
graphs shown with the corresponding plan name.
3. Label the axes with words and values (see the window settings – put the xmin, xmax,
ymin and ymax values on the graph above).
4. Graph the cost of the Rover package in Y1 and the Crystal Net package in Y2.
Ring Mobility should not be on the screen. To determine when the cost is the same use
the intersect function on the graphing calculator.
Here are the steps (follow them closely)
 2nd TRACE (CALC option)
 5: intersect
 First Curve? Will appear on your screen…press ENTER
 Second Curve? ENTER
 Guess? ENTER
What are the values for x? _____ and y? _____ What does this mean?
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DECISIONS, DECISIONS, DECISIONS
The following questions should be done on a separate piece of paper.
5. Use the intersect function to determine for which time value the cost of the Rover
package and the Ring Mobility package is the same.
6. Use your graph to determine for which time values Ring Mobility is a better deal than
both Rover and Crystal Net. Explain your selection.
7. If your friend expects to use her cell phone between 40 and 100 minutes per month,
explain to her which service you think she should choose.
8. MARKET SHARE is the number of customers selecting your product.
If you were in charge of marketing for Ring Mobility and it was your goal to increase your
market share, how could you adjust your pricing formula to attract customers from the
other two companies? You will need to change the equation for Ring Mobility.

State the equation for your new pricing structure. Explain the decisions you made
in forming your equation, remembering that you have to make money for the
company as well as attract as many customers as possible.
My equation is:

Provide graphical support for your new pricing structure.
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