i missed this lesson, skiing that day, and am wondering if im doing this right

the question is:

Find the volume of the solid that results when the region enclosed by the given curves is revolved around the given axis.

y=√x, y=0, x=0, x=4; about y=2

i wrote it as pi times the integral, from 0 to 4, of 2^2-(√x)^2

and got 8pi

can anyone confirm, or refute that? or offer some help

thanks for good info