Car B is traveling a distance d ahead of car A. Both cars are traveling at 60 ft/s when the driver of B suddenly applies the breakes, causing his car to decelerate at 12 ft/s^2. It takes the driver of car A 0.75 s to react. When he applies his brakes, he decelerates at 15 ft/s^2. Determine the minimum distance d between the cars so as to avoid a collision