Originally Posted by EIQuilter

I think I'd cut the three large pieces all to the same length - 88". Then I'd take the 72" piece and cut strips 16"xWOF. Add a 16" strip to the "top" of the first large piece, another to the "bottom" of the second large piece, and another to the "top" of the third large piece. That will give you three pieces that are approximately WOF x 103". Sew each of those three pieces together along the selvage edge, and you'll end up with a backing piece that is approximately 103"x120", plenty big enough for a 94"x112" top.

Good luck!