Let R denote the region enclosed by the y-axis, the line y = 1, and the curve

y = sqrt(x). Compute the volume of the solid whose base is R and whose cross sections perpendicular to the y-axis are semicircles.

I don't get it.. i did integral(pi*(y^2)^2)dy) from y=0 to y=1. i got pi/10

The answer is supposed to be pi/40.