The conical watering pail has a grid of holes. Water flows out through the holes at a rate of kA m3/min, where k is a constant and A is the surface area of the part of the cone in contact with the water. This surface area is A = πr √(h2 + r2) and the volume is v = 1/3 πr2h. Calculate the rate dh/dt at which the water level change at h = 0.18 m, assuming that k = 0.25 m.
