4. Find the area of the surface generated by revolving about the x-axis the curve f(x) = 2vx-1 on [1, 4]. 5. The spherical tank in Fig. 21 is full of water. How much work is done lifting the water to the top of the tank? radius = 4 ft Fig. 21 6. Calculate the centroid of the region (use Simpson's rule with n = 20 if necessary) y = x2 and the line y = 2x for 0