1. In how many ways can two squares be selected from an 8-by-8 chessboard so that they are not in the same row or the same column.

2. In how many ways can we place r red balls and w white balls in n boxes so that each box contains at least one ball of each colour.

3. Find a formula for $\displaystyle \binom{n}{0}^2+\binom{n}{1}^2+\binom{n}{2}^2+...+\ binom{n}{n}^2$

Thanks