(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.

(b) Set up an integral to find the area of the surface generated by rotating the curve y = √x, 0 ≤ x ≤ 4, about the line y = 4. Then evaluate the integral numerically, correct to four decimal places.