\(\eqalign{\frac{{\left( {\begin{array}{*{20}{c}}
{10}\\
2
\end{array}} \right)\left( {\begin{array}{*{20}{c}}
8\\
2
\end{array}} \right)\left( {\begin{array}{*{20}{c}}
6\\
2
\end{array}} \right)\left( {\begin{array}{*{20}{c}}
4\\
2
\end{array}} \right)}}{{5!}} = 945}\)