more bsat questions

Bob has become aroused. Unlike most, his penis is shaped like a perfect cylinder. The head of his dick contains a fixed amount of blood regardless of his flaccidity. His shaft starts with a length of 3 inches and a radius of 1 inch. His penis grows at 0.25 inches per second in length, and 0.0625 inches per second in radius. At the exact instant his shaft is 5 inches in length, find the rate at which the volume of blood in his dick is increasing.