Find the total number of rectangles on the normal chessboard.

Explanation

To form a rectangle on a chessboard two vertical lines and two horizontal lines should be selected. There are 9 vertical lines and 9 horizontal lines found on the chessboard. Selection of 2 vertical and 2 horizontal lines can be done in `.^(9)C_(2)xx .^(9)C_(2)` ways, which is equivalent to the number of rectangles.