8 The height, \(h\) metres, of a shrub \(t\) years after planting is given by the differential equation
$$\frac { \mathrm { d } h } { \mathrm {~d} t } = \frac { 6 - h } { 20 }$$
A shrub is planted when its height is 1 m .
- Show by integration that \(t = 20 \ln \left( \frac { 5 } { 6 - h } \right)\).
- How long after planting will the shrub reach a height of 2 m ?
- Find the height of the shrub 10 years after planting.
- State the maximum possible height of the shrub.