Answer
$ -183.75J$
Work Step by Step
The initial potential energy of the ball relative to the ground will be:$Ep_{0}=mgh\left.......( 1\right) $.
On the ground:
$Ep_{1}=0\left......( 2\right) $ because there is no height difference relative to the ground.
So the energy change of snowball during flight will be: $\Delta E_{p}=Ep_{1}-Ep_{0}=-mgh(3)\approx -183.75J$.
Lets assume the potential energy at the top is zero ($E_{p0}=0$).
Using (3), we get
$\Delta E_{p}=Ep_{1}-Ep_{0}=-mgh\Rightarrow -mgh=Ep_{1}-0\Rightarrow Ep_{1}=-mgh\approx -183.75J$
