5. The height of water, \(H\) metres, in a harbour on a particular day is given by the equation
$$H = 10 + 5 \sin \left( \frac { \pi t } { 6 } \right) , \quad 0 \leqslant t < 24$$
where \(t\) is the number of hours after midnight.
- Show that the height of the water 1 hour after midnight is 12.5 metres.
- Find, to the nearest minute, the times before midday when the height of the water is 9 metres.