7. A train travels along a straight horizontal track between two stations \(A\) and \(B\). The train starts from rest at \(A\) and moves with constant acceleration until it reaches its maximum speed of \(108 \mathrm {~km} \mathrm {~h} ^ { - 1 }\). The train then travels at this speed before it moves with constant deceleration coming to rest at \(B\). The journey from \(A\) to \(B\) takes 8 minutes.

1. Change \(108 \mathrm {~km} \mathrm {~h} ^ { - 1 }\) into \(\mathrm { m } \mathrm { s } ^ { - 1 }\).
2. Sketch a speed-time graph for the motion of the train between the two stations \(A\) and \(B\). Given that the distance between the two stations is 12 km and that the time spent decelerating is three times the time spent accelerating,
3. find the acceleration, in \(\mathrm { m } \mathrm { s } ^ { - 2 }\), of the train.