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Calling Plan: Monthly Cost

The monthly cost in dollars of a long-distance phone plan is a linear function of the total calling time in minutes. The monthly cost for 42 minutes of call is $16.42 and the monthly cost for 88 minutes is $21.48. What is the monthly cost for 64 minutes?

Solution Preview

We can assume that the linear equation is


Given C(42)=$16.42 and C(88)=$21.48. So,

16.42=a+42b ...

Solution Summary

A linear equation is used to find the cost of a calling plan.