Volume of an object rotated on x-axis

Hi guys and girls,, this is my first post here so hi to everybody ! :)

Ok my questions is how do i calculate the volume of an object rotated on the x-axis

I have two functions f(x) = 2*sqrt(x) & g(x) = 8-x

fist i calculate the area from 0 to 4(Their intersection)

aw = g(x) - f(x)
int(aw, 'x', 0, 4)

it spits out : 40/3 which is correct

Now i have to rotate it against? the x-axis and calculate the volume

V = pi * int(aw^2, 'x', 0, 4)
V =

(928*pi)/15

Which is not the same answer as i have on my page with answers
The result on the page is : (352*pi)/3

What am i doing wrong? :(

Sorry for my english
Thankes !