1. A team of scientists is studying a species of slow growing tree.

The rate of change in height of a tree in this species is modelled by the differential equation

$\frac{dh}{dt}=\frac{{t}^{0.25}(4-\sqrt{h})}{20}$

where $h$ is the height in metres and $t$ is the time, measured in years, after the tree is planted.

Find, according to the model, the range in heights of trees in this species.