Contour Enthusiasts Group Archives Forums Modifications Audio Enclosure Volume, Help

I have a enclosure that I bought at a yard sale. Actually it was well made, 3/4 MDF, glued and screwed, never been used. I normally build my own but a broken left arm made that impossible. It has been so long since I built one I have forgotten how to figure the volume of the enclosue. The inside measurements are as follows, BTW it is in a triangle shape so the top and botom measurements are different.
13 1/2 X 6 X 10 X 33. Thanks for your help.

~2.06

Take the rectangle 13.5x6x33 Then take (13.5x4x33)/2 add the two numbers divide by 1728