ft A spherical balloon is inflating with helium at a rate of 64x - min How fast is the balloon's radius increasing at the instant the radius is 2 ft? Write an equation relating the volume of a sphere, V, and the radius of the sphere, r. (Type an exact answer, using x as needed.) Differentiate both sides of the equation with respect to t. dv dt Type an exact answer, using a 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 2 ft. (Simplify your answer.)