The diagram is the speed-time graph of part of a train's journey. [Figure X.X] The train slows down uniformly from a speed of u m/s to a speed of 6 m/s in 10 seconds. During the next 20 seconds it travels at a constant speed of 6 m/s. It then slows down uniformly to a stop after a further 30 seconds.

1. (a)Calculate the retardation from t = 30 to t = 60.[1]
2. (b)Calculate the speed of the train when t = 40.[1]
3. (c)The distance travelled by the train from t = 0 to t = 10 is 85 m. Find u.[2]

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