A water tank has a shape of an inverted right circular cone with its axis vertical and vertex lower most. Its semi vertical angle is $\tan^{-1} (0.5)$.Water is poured into it at a constant rate of 5 cubic meter per hour. Find the rate at which the level of the water is rising at the instant when the depth of water in the tank is $4\; m$

Question

$\begin{array}{1 1} \frac{35}{88}m/hr \\ \frac{50}{41}m/hr \\ 1 \\ 0 \end{array} $