Assume that the radius rr of a sphere is expanding at a rate of 19 in./min.19 in./min. the volume of a sphere is v=43πr3v=43πr3. determine the rate at which the volume is changing with respect to time when t=5 min. t=5 min. assuming that r=4r=4 at t=0t=0. the volume is changing at a rate of