A solid lies between planes perpendicular to the x-axis at x= 0 and x =9. The cross-sections perpendicular to the axis on the interval 0s x$9 are squares with diagonals that run from the parabola y = - 2vx to the parabola y=2vx. Find the volume of the solid. The volume of the solid is cubic units. (Type an exact answer, using it as needed.)