Rate of change: \( \frac{dV}{dt} = -0.2\sqrt{h} \); but \( \frac{dV}{dt} = \frac{dV}{dh} \cdot \frac{dh}{dt} = \frac{25\pi}{432} \cdot 3h^2 \frac{dh}{dt} = \frac{25\pi}{144} h^2 \frac{dh}{dt} \).