Answer :

AL2006

Circles don't have volume, but they do have area. 
The area of any circle is ...

                         (pi) x (the circle's radius)² .

The circle's radius is 1/2 of its diameter.

So for the circle in the question,

Radius = 30-ft

Area = (pi) x (900 square ft) = 2,827 square feet  (rounded)