In a cross-hatched grid, a total of different rectangles could be situated within that grid as indicated in the sketch.
There are grids smaller than , vertical and horizontal dimensions being important, i.e. , , , and . If each of them is cross-hatched, the following number of different rectangles could be situated within those smaller grids:
Adding those to the of the grid, a total of different rectangles could be situated within and smaller grids.
How many different rectangles could be situated within and smaller grids?
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