You need two that are 80 inches long, then two that are 102 long (90 plus 6 plus 6). That's a total of 364 inches. Assuming you can get a 40 inch length out of each WOF, you need 9.1 cuts. I use 40 when doing this math as it allows for a straight butted seam.(because fabric is usually 42) If you plan on a bias seam in your border (rarely is this done on a wide border) then you need to add about 20 inches per seam to the total. Does that help? As for how much fabric you need, that's 9 cuts of 6.5 inches each, a total of one and five eighths yards.