so hmm check the picture below....notice that r = h/2
thus [tex]\bf V=\cfrac{1}{3}\pi r^2 h\qquad
\begin{cases}
d=h\\
r=\frac{d}{2}=\frac{h}{2}
\end{cases}\implies V=\cfrac{1}{3}\pi \left( \cfrac{h}{2} \right)^2h
\\\\\\
V=\cfrac{\pi }{3}\cdot \cfrac{h^2}{2^2}\cdot h\implies V=\cfrac{\pi }{12}h^3\\\\
-----------------------------\\\\
\cfrac{dV}{dt}=\cfrac{\pi }{12}\cdot 3h^2\cfrac{dh}{dt}\implies \cfrac{dV}{dt}=\cfrac{\pi }{4}h^2\cfrac{dh}{dt}\implies \cfrac{4\frac{dV}{dt}}{\pi h^2}=\cfrac{dh}{dt}[/tex]
and keeping in mind that [tex]\bf \cfrac{dV}{dt}=50[/tex], surely you already know what [tex]\bf \left. \cfrac{dh}{dt}\ \right|_{h=14}[/tex] is
