39. (a) If the curve y = f(x), a = x = b, is rotated about the horizontal line y = c, where f (x) = c, find a formula for the area of the resulting surface. T (b) Set up an integral to find the area of the surface generated by rotating the curve y Vx, Q Ex = 4, about the line y = 4. Then evaluate the integral numerically, correct to four decimal places