Answer
The release height is
$$h=1.20\text{ m}.$$
Work Step by Step
We can determine the required height as follows:
$H=(\frac{u tan30^{\circ}}{\sqrt{\frac{g}{2}}})^2$
We plug in the known values to obtain:
$H=(\frac{(4.20)tan 30^{\circ}}{\sqrt{\frac{98}{2}}})^2$
This simplifies to:
$H=1.20m$
