I am totally confused about this problem...

Suppose that we pump water into an inverted right-circular conical tank at the rate of 5 cubic feet per minute (i.e., the tank stands point down.) The tank has a height of 6ft and the radius on top is 3ft. What is the rate at which the water level is rising when the water is 2ft deep? (Note that the volume of a right circular cone of radius $\displaystyle r$ and height $\displaystyle h$ is $\displaystyle V = \frac{1}{3}\pi r^2h$.