An inverted square pyramid 20 ft high with a square base having 8-foot sides is filled with oil at the rate of 2 cubic ft/s. How fast is the oil rising when it is at 4 ft deep? Volume of square pyramid: , where A = area of the base, h = height.

A.

0.313 ft/s

B.

0.625 ft/s

C.

0.78 ft/s

D.

1.25 ft/s