For Exercises 2.44 and 2.45, see page 82; for 2.46, see page 84; for 2.47, see page 86; for 2.48 and 2.49, see page 88; for 2.50, see page 90; for 2.51, see page 90; for 2.52, see page 91; and for 2.53, see page 94.

Question 2.57

2.57 Compare the cell phone payment plans

A cellular telephone company offers two plans. Plan A charges $30 a month for up to 120 minutes of airtime and $0.55 per minute above 120 minutes. Plan B charges $35 a month for up to 200 minutes and $0.50 per minute above 200 minutes.

  1. Draw a graph of the Plan A charge against minutes used from 0 to 250 minutes.
  2. How many minutes a month must the user talk in order for Plan B to be less expensive than Plan A?

2.57

(b) Plan B gets cheaper at 130 minutes.