<p>here it is:
There are exactly 4 actors which try out for the 4 parts in a play. If each actor can preform any one part and no one will perform more than one part, how many different assignments of actors are possible?</p>
<p>I'm not really familiar with the whole idea of factorials, but just based on what the answer was, I knew it had to do with factorials. Study up on factorials, permutations, and combinations.</p>