Taking into account reaction time, the distance d (in feet) that a car requires to come to a complete stop while traveling r miles per hour is given by the function

d(r) = 6.97r - 90.39

(a) Express the speed r at which the car is traveling as a function of the distance d required to come to a complete stop.

(b) Verify that r = r(d) is the inverse of d = d(r) by showing that r(d(r)) = rand d(r(d)) = d.

(c) Predict the speed that a car was traveling if the distance required to stop was 300 feet.