Sand falls from a cenveyar belt and accumulates in a ennical pile whase radius is always mine its height. The sand falls at a constant rate of 1 n13is {a} Find the rate at which the height of the pile is increasing when the pile is 3m high. Him: The 1irculunie of a cone with base radius r and height h is V = in? h. (h) Find the rate at which the surface area cf the pile is increasing when the pile is 3m high. Hint: The surface area [excluding base) of cane with base radius r and height h is A = an? r2 + hi