A drag racer accelerates from rest at an average rate of +13.2 m/s² for a distance of 100 m. The driver coasts (drives with constant velocity) for 0.5 seconds and then uses the brakes and parachute to decelerate until the end of the track. If the total length of the track is 180 m, what minimum acceleration rate must the racer have in order to stop prior to the end of the track?