Question

A basic cellular package costs $20/month for 60 minutes of calling with an additional charge of$0.20/minute beyond that time. The cost function C (a) for using a minutes would be• If you used 60 minutes or less, i.e. if if a < 60, then C (a) = 20 (the base charge).• If you used more than 60 minutes, i.e. (- 60 minutes more than the plan came with, you wouldpay an additional $0.20 for each of those (I60) minutes.Your total bill would beC(I) = 20 + 0.20 (2 - 60).If you want to keep your bill at $50 or lower for the month, what is the maximum number of callingminutes you can use?The maximum calling minutes you can use is ________ minutes

Answer 1

`\begin{gathered} \text{The cost for more than 60 minutes is} \\ x=\text{ number of minutes } \\ C(x)=20+0.2(x-60) \\ 50=20+0.2(x-60) \\ \text{Solving x} \\ 50=20+0.2x-12 \\ 50-20+12=0.2x \\ 42=0.2x \\ x=(42)/(0.2) \\ x=210 \\ \text{The maximum calling minutes you can use is 210 minutes} \end{gathered}`