fts A spherical balloon is inflating with helium at a rate of 144x How fast is the balloon's radius increasing at the instant the radius is 3 ft? min Write an equation relating the volume of a sphere, V, and the radius of the sphere, r. (Type an exact answer, using it as needed.) Differentiate both sides of the equation with respect to t. dv dt (Type an exact answer, using it 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.)