A tanker that ran aground is leaking oil that forms a circular slick about 0.2 foot thick. To estimate the rate dV/dt (in cubic feet per minute) at which oil is leaking from the tanker, it was found that the radius of the slick was increasing at 0.31 foot per minute (dR/dtequals0.31) when the radius R was 400 feet. Find dV/dt, using pi almost equals 3.14 .