A subway car leaves station A; it gains speed at the rate of 2 m/s^2 for 6 seconds and then at the rate of 3 m/s^2 until it has reached the speed of 24m/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 seconds. The total running time from A to B is 40 seconds. Draw the a-t, v-t, and x-t curves, and determine the distance between stations A and B.