Chapter 2.2, Problem 96E

A telephone company offers the following plans. Also given are the piecewise functions that model these plans. Use this information to solve Exercise 95–

Plan A

 $30 per month buys 120 minutes.

 Additional time costs $0.30 per minute.

$C(t)=\{\begin{array}{cc}30& \text{if}\\ 30+0.30(t-120)& \text{if}\end{array}\begin{array}{c}\text{0}\le t\le \text{120}\\ t\text{ >120 }\end{array}$

Plan B

 $40 per months buys 200 minutes.

 Additional time costs $0.30 per minute.

$C(t)=\{\begin{array}{cc}40& \text{if}\\ 40+0.30(t-120)& \text{if}\end{array}\begin{array}{c}\text{0}\le t\le \text{200}\\ t\text{ > 200 }\end{array}$

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