Some enterprising physics students working on a catapult decide to have a water balloon fight in the school hallway. The ceiling is of height $3\mathrm{.}5$ m$,$ and the balloons are launched at a velocity of $11$ m$/$s$.$The acceleration of gravity is $9\mathrm{.}8$ m$/?$At what angle must they be launched to$$ust graze the ceiling?Answer in units of $\backslash$deg

Pls answer with thorough explanation