Chapter 8.4, Problem 43E

Speeding Fines Speeding fines are determined by

$f(x)=10(x-65)+50,x>65,$

where f(x) is the cost, in dollars, of the fine if a person is caught driving x miles per hour.

(a) Radar clocked a driver at 76 mph. How much was the fine?

(b) While balancing his checkbook, Johnny ran across a canceled check that his wife Gwen had written to the Department of Motor Vehicles for a speeding fine. The check was written for $100. How fast was Gwen driving?

(c) At what whole number speed are tickets first given?

(d) For what speeds is the fine greater than $200?