Two cars on a rotating observation wheel

The height, \(h\) metres, of car \(A\) on an observation wheel \(t\) minutes after it is at the lowest point is modelled by \(h=30-25\cos\left(\dfrac{\pi t}{10}\right)\). Car \(B\) is a quarter of a revolution behind car \(A\). Assume the wheel turns at a constant rate.

1. Find the time for one revolution, and the fraction of each revolution for which car \(A\) is more than \(42.5\) m above the ground.[3]
2. Show that the height of car \(B\) is \(30-25\sin\left(\dfrac{\pi t}{10}\right)\).[2]
3. Find the times in \(0\le t\le 20\) at which the two cars are at the same height, and explain why this happens twice per revolution.[3]