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 .