You testify as expert witness in a case involving an accident in which car A slid into the rear of car B, which was stopped at a red light along a road headed down a hill (Fig.3-15). You find that the slope of the hill is , that the cars were separated by distance when the driver of car A put the car into a slide(it lacked any automatic antibrake-lock system), and that the speed of car A at the onset of braking was With what speed did car A hit car B if the coefficient of kinetic friction was (a) (dry road surface ) and (b) (road surface covered with wet leaves )?