In a $999 × 999$ square table some cells are white and the remaining ones are red. Let $T$ be the number of triples $(C_1, C_2, C_3)$ of cells, the first two in the same row and the last two in the same column, with $C_1$ and $C_3$ white and $C_2$ red. Find the maximum value T can attain. The original answer is in \frac{m}{n} format, please give the value of m + n.

Let's think step by step and output the final answer within \boxed{}.
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