Here is the question:

A solid is formed by rotating the region bounded by the curve and the -axis between and , around the -axis. The volume of this solid is . Assuming the solid has constant density , find and .

To find the moment, I did:

=

As density was constant, I divided the moment by the volume and found to be 1/2.

And I am not sure that is right and so I haven't even attempted to find . All help is much appreciated. Thanks.