The flowerpot shown in the sketch has a uniform thickness of 3in. and is 1ft high. Find the amount of material necessary to construct 1000 such pots. (Neglect the drain in the bottom)

What I did is get the volume of the bigger frustum which results to:

V = [h(18^2 + 12^2 + sqrt (18 * 12))]/3

V = 1930.79 cu. in

I don't know now the next step...

the answer should be1098 cu. ft.

Help please THANKS!