3. Define a variable, write an equation, and solve.
One cell phone plan costs $39.95 per month. The first 500 minutes of usage are
free. Each minute thereafter costs $.35. Write a rule that describes the total
monthly cost as a function of the number of minutes of usage (over 500
minutes).Then find the number of minutes of usage over 500 minutes for a bill of
$69.70.
A C = 39.95 +0.35m; 64 min
B 39.95 = 0.35m: 114 min
Cc = 39.95 + 0.35m: 85 min
DC=0.35 + 39.95m: 1.7 min