A circle has an initial radius of 50 ft when the radius begins decreasing at the rate of 3 ft/min. What is the rate in the change of area at the instant that the radius is 16 ft? Write an equation relating the area of a circle, A, and the radius of the circle, r. (Type an exact answer, using to as needed.) Differentiate both sides of the equation with respect to t. dA dr dt D dt (Type an exact answer, using x as needed. Type an expression using r as the variable.) The rate of change of the area is (Type an exact answer in terms of it.)