Help please.

A cylindrical iron ring has a height of 18 inches. The outside diameter is 120 inches while the inside diameter is 90 inches. What is the weight of the iron ring if 1 cubic feet measures 640 pounds.

Uhmm, this is what I did. I solve for the volume of the two rings(outside and inside). Then I add them together, then convert into cubic feet, then pounds. Is that right?