how to find the volume of a figure with this cross section

Hello, I need to figure out how to find the volume of this shape with a cross-sectional area that looks like this. This shape is rotated around a central axis to make a "ring".:

http://img641.imageshack.us/img641/3...barrelring.png

It is basically a triangle, but the hypotenuse is a small portion of a much larger circle instead of a straight line.

In order to find the volume of this "ring", I would first need to find the area of this shape, A. I would also need to find the center of gravity x-coordinate of the shape. Cgx I'll call it.

Once I have that information, I'd be able to find the volume of this ring. The volume would be:

Vr = 2*pi*A*(D+Cgx), where D is the distance from the center axis to the right leg of the shape.

I don't know how to find A or Cgx though...Can anyone help me with this please? Thanks a lot!