fluid is entering a spherical tank with a 6 inch radius at a constant rate of 30 pi cubic inches per hour. when the water is h feet deep, the volume of the water in the tank is given by:

V = [(pi)(h^2)/3] (18-h)

what is the rate at which the depth of the water in the tank is increasing at the moment when the water is 2 inches deep?

thanks so much i really appreciate it! im so confused on this one!