(For assistance with this exercise, refer to the discussion of piecewise functions beginni...

(For assistance with this exercise, refer to the discussion of piecewise functions beginning on, as well as to Exercise 1-2.) Group members who have cellphone plans should describe the total monthly cost of the plan as follows:

(For simplicity, ignore other charges.) The group should select any three plans, from “basic” to “premier.” For each plan selected, write a piecewise function that describes the plan and graph the function. Graph the three functions in the same rectangular coordinate system. Now examine the graphs. For any given number of calling minutes, the best plan is the one whose graph is lowest at that point. Compare the three calling plans. Is one plan always a better deal than the other two? If not, determine the interval of calling minutes for which each plan is the best deal. (You can check out cellphone plans by visiting www.point.com.)

Exercise 1

Simplify the algebraic expression in the second line of the piecewise function for plan A. Then use point-plotting to graph the function.

Exercise 2

Simplify the algebraic expression in the second line of the piecewise function for plan B. Then use point-plotting to graph the function.