How to give the differential equation relating to the rate of change of the volue WRT the rates of change of the height and radius. Then what is the rate of change of the volume at the instant for the given height and radius.

34. The height of a right-circular cylinder is decreasing at the rate of 18 cm/min and the radius is increasing at the rate of 21 cm/min. Find the rate of change of the volume at the instant when the height is 250 cm and the radius is 65 cm. Give the wire diagram relating the rates of change of volume, radius, and height with respect to time in the space provided on the answer sheet. Give the differential equation relating the rate of change of the volume WRT the rates of change of the height & radius (line 1) then answer the question (line 2)