The plane is revolving about the -axis.

(a)

Shell method:

The volume of a solid of revolution with the shell method Vertical axis of revolution is, .

The rectangle in shell method is .

The rectangles would be vertical.

(b)

Disk method:

The volume of a solid of revolution with the disk method:

Vertical axis of revolution, .

The rectangle in disk method is .

The rectangles would be horizontal.

(a) The rectangles would be vertical.

(b) The rectangles would be horizontal.