This is LaTeX code:
[latex]
S_{XY}=3\cdot3\cdot5 + 3\cdot4\cdot5 + 3\cdot5\cdot2 + 4\cdot3\cdot2 + 4\cdot4\cdot10 + 4\cdot5\cdot2 + 3\cdot3\cdot5 + 5\cdot3\cdot2 + 5\cdot4\cdot5 + 5\cdot5\cdot5 - 38\cdot4\cdot4 = = 614 - 608 = 6
[/latex]