A train travelling along a straight track starts from rest at piont A and accelerates uniformly to 20ms' in 20s. it travels at this speed for 60s, then slows down uniformly to rest in 40s at point C. it stays at rest at C for 30s, then reverses direction, accelerating uniformly to 10ms' in 10s. it travels at this speed for 30s, then slows down uniformly to rest in 10s When it reaches point B. plot a graph of the motion of the train.