A X B A subway car leaves station A; it gains speed at the rate of 4 ft/s for 6 s and then at the rate of 6 ft/s until it has reached the speed of 48 ft/s. The car maintains the same speed until it approaches station B; brakes are then applied, giving the car a constant deceleration and bringing it to a stop in 6 s. The total running time from A to B is 40 s. Draw the a-t, v-t, and x-t curves, and determine the distance between stations A and B.