Find the volume of the solid whose base is the region between the x-axis and the inverted parabola f(x)=4-x^2 if every vertical cross sections of the solid perpendicular to the y-axis are semicircles.
Find the volume of the solid whose base is the region between the x-axis and the inverted parabola f(x)=4-x^2 if every vertical cross sections of the solid perpendicular to the y-axis are semicircles.