Answer
6.75 J
Work Step by Step
We found in part (c) that $\Delta U=U_{2}-U_{1}=6.75\,J$
If the gravitational potential energy at the launch point $U_{1}=0$
Then, $U_{2}-0=6.75\,J$
i.e., gravitational potential energy at the maximum height $U_{2}=6.75\,J$
