(a) If A is the area of a circle with radius r and the circle expands as time passes, find A in terms of of dt dt dA dr dt dt (b) Suppose oil spills from a ruptured tanker and spreads in a circular pattern. If the radius of the oil spill increases at a constant rate of 2 m/s, exactly how fast (in m2/s) is the area of the spill increasing when the radius is 22 m? m2/s