#### Problem 29E

29. Gravel is being dumped from a conveyor belt at a rate of $30 \mathrm{ft}^{3} / \mathrm{min}$, and its coarseness is such that it forms a pile in the shape of a cone whose base diameter and height are always equal. How fast is the height of the pile increasing when the pile is $10 \mathrm{ft}$ high?