Connected Rates for a Conical Sand Pile

Sand is poured onto a horizontal surface to form a right circular conical pile. The radius of the base of the pile is always \(\frac{3}{4}\) of its vertical height. The volume of the pile is increasing at a constant rate of \(10\text{ cm}^3\text{/s}\). Find the rate at which the curved surface area of the pile is increasing at the instant when its height is \(4\text{ cm}\).[5]