5. A vertical ladder is fixed to a wall in a harbour. On a particular day the minimum depth of water in the harbour occurs at 0900 hours. The next time the water is at its minimum depth is 2115 hours on the same day. The bottom step of the ladder is 1 m above the lowest level of the water and 9 m below the highest level of the water. The rise and fall of the water level can be modelled as simple harmonic motion and the thickness of the step can be assumed to be negligible. Find

1. the speed, in metres per hour, at which the water level is moving when it reaches the bottom step of the ladder,
2. the length of time, on this day, between the water reaching the bottom step of the ladder and the ladder being totally out of the water once more.