As sand leaks out of a hole in a container, it forms a conical pile whose altitude is always the same as its radius.

As sand leaks out of a hole in a container, it forms a conical pile whose altitude is always the same as its radius. If the height of the pile is increasing at the rate of 8 in/min, find the rate (in cubic inches per minute) at which the sand is leaking out when the height is 10 in.