I have been attempting to do the question with different methods.

I can do this question by the shells method, but I want to know how to do it by volumes by slicing/washer method.

Question:

A circle of radius 2 is given by $\displaystyle x^2+y^2 = 4$ and is revolved about the line $\displaystyle x=5$. Using the washer/volume by slicing method, prove that the resulting volume (a TORUS) is $\displaystyle 40 {\pi}^2$.

Any help would be greatly appreciated!