Bunker Hill Monument is a stone structure in the form of the frustum of a regular square pyramid whose height is 220ft. and whose base edges are 15ft. and 30ft., respectively. Through the center of the monument is a cylindrical opening 11ft. in diameter at the top and 15ft. in diameter at the bottom. Find the volume of the stone in the monument.

The Answer in the back of the book Solid Mensuration by Kern and Bland is86,068 cubic feet.

I don't have a diagram for this. Please help i don't know the solution for this