12. The hypotenuse AB of a right triangle ABC is 5 ft, and one leg, AC, is decreasing at the rate of 2 /see The rate, in square feet per second, at which the area is changing when AC = 3 is 13*. Find the volume ofthe solid whose base is the region bounded between the curves y = x and y =x2 , and whose cross sections perpendicular to the xaxis are squares. 14*. The base of a certain solid is the region enclosed by y = \\l; , y = 0, and x = 4. Every cross section perpendicular to the XaXlS is a semicircle with its diameter across the base. Find the volume of the solid. 1. Find the volume of the solid generated when the region enclosed between y = \\I; , x = 1, x = 4, and the xaxis is revolved about the ycaxis