The volume of the solid is .

(a)

The volume of the solid using shell method: .

Here height is , radius is and thickness is .

Plane region bounded by curves , and . 

(b)

and thickness is .

Because the thickness that means integrate along the -axis.

For the shell method integrating along mean the axis of revolution is about the line .

(a) Plane region bounded by equations , and .

(b) The axis of revolution is about the line .