At a sand gravel plant, sand is falling off a conveyor and onto a conical pile at a rate of 10 cubic feet per minute. The radius of the base of the cone is twice the height. At what rate is the height of the pile changing when the pile is 5 feet high. Note: The volume of a cone is V = (/3)r 2 h where r is the radius of the base and h is the height of the cone. (