7) A block of ice, in the shape of a cylinder, is melting such that both its radius and its height are decreasing at the rate I cm/min. ( This means that r'= - 1 im/min and h' = - 1 (m/min). How fast is the volume of the cylinder decreasing when r= 10 cm and h= 20 cm? 1 the formula for the volume of a cylinder is V= Trzh)