Hey all,

The following question was covered in a logic class, its somewhat fairly easy but I am finding it hard to grasp the concepts.

So let $\displaystyle \sum = \{\alpha ,\beta ,\gamma ,\delta \} $ be an alphabet, I want to find how many elements they are in $\displaystyle \sum^5$ such that $\displaystyle \alpha$ and $\displaystyle \gamma $ occur exactly once.