Kinda lost right here, please help, thanks.

A spherical balloon is inflating with helium at a rate of 72x f1 3 min . How fast is the balloon's radius increasing at the instant the radius is 3 ft? Write an equation relating the volume of a sphere, V, and the radius of the sphere, r. (Type an exact answer, using n as needed.) Differentiate both sides of the equation with respect to t. dV dt at (Type an exact answer, using x as needed. Type an expression using r as the variable ) The balloon's radius is increasing at a rate of at the instant the radius is 3 ft. (Simplify your answer.) ftz / min fts / min Enter your answer in each of the answer boxes ft / min