The radius of a right circular cylinder is increasing at a rate of 2 units per second. The height of the cylinder is decreasing at a rate of 5 units per second. Which of the following expressions gives the rate at which the volume of the cylinder is changing with respett to time in terms of the radius r and height h of the cylinder? (The volume V of a cylinder with radius r and height h is V = Ttrh.) (A) -2011r (B) -21trh (C) 4itrh - 570r (D) 4trh+ 51tr