A train runs at a constant speed of 20m/s for 300s. and then accelerates uniformly to a speed of 30m/s over a period of 20s, this speed is maintained for 300s before the train is brought to rest with a uniform deceleration is 30s.

1. draw the velocity time graph to represent the journey described above.
2. From the graph find the acceleration while the speed changes from 20m/s to 30m/s