Fixed Point Limit I

Let $F_n$ be the number of fixed points of a random function $f: S_n \rightarrow S_n$, where $S_n = \{1,2,\dots,n\}$. Find $\displaystyle \lim_{n \rightarrow \infty}\mathbb{P}[F_n = 5]$. The answer is in the form $\dfrac{c}{e}$, where $e$ is Euler's constant and $c$ is a constant. Find $c$.