. . 2 The area of a circle Increases at a rate of 4 cm Is. a. How fast is the radius changing when the radius is 6 cm? b. How fast is the radius changing when the circumference is 3 cm? a. Write an equation relating the area of a circle, A, and the radius of the circle, r. 2 A=TEF (Type an exact answer, using 11: as needed.) Differentiate both sides of the equation with respect to t. dA dr a - (\"