A 108m long train starts from rest (at t=0) and accelerates uniformly. At the same time (at t=0), a car moving with constant speed in the same direction reaches the back end of the train. At t=12 s the car reaches the front of the train. However, the train continues to speed up and pulls ahead of the car. At t=32 s, the car is left behind the train. Determine
a) the car's speed
b) the train's acceleration.