a long distance cell phone company charges .99 for the first 20 min or less of a call. (ex: 15 mins cost .99) and 7 mins for every min thereafter

Question

a long distance cell phone company charges .99 for the first 20 min or less of a call. (ex: 15 mins cost .99) and 7 mins for every min thereafter

1. Write a precise definition of the charge f(x) of a call lasting x mins

Answer 1

f(x) = 0.99 if x ≤ 20

f(x) = 0.99 + 0.07x if x > 20