I'm trying to help a friend w/ calc but it's been a long time since i've done it. it's on partial derivatives. Any help is appreciated!!!:

The function S(w, h) = (15.63w^0.425) * (h^.0725) gives the approximate surface area (in sq. inches) of a person h inches tall who weighs w pounds.

1) At his full height of 5'9", he goes to the gym and bulks up. At what rate is his body surface increasing when he reaches 140 pounds?