If three squares are selected at random from a chessboard, then the probability that they form the letter L is
1
\( \frac{196}{{ }^{64} \mathrm{C}_3}\)
2
\( \frac{49}{{ }^{64} \mathrm{C}_3}\)
3
\( \frac{36}{{ }^{64} \mathrm{C}_3}\)
4
\( \frac{98}{{ }^{64} \mathrm{C}_3} \)