3. (30points) Use an iterated double integral to answer each of the following question. (a) (8 points) D is the triangle with vertices (0, 0), (1, 1) and (0, 4), compute JJp T dA. (b) (10 points) Compute the mass of the lamina in the xy-plane, enclosed by a" ty = 1, above y = r and y = -r. The density function is p(x, y) = 23. Hint; the region of integration should be above the x-axis. (c) (12 points) Compute the area of the plane 2x + 2y + z = 6 above the region enclosed by r = cos(0) in the xy-plane