Determine whether Rolle's Theorem can be applied to $f$ on the closed interval $[a, b] .$ If Rolle's Theorem can be applied, find all values of $c$ in the open interval $(a, b)$ such that $f^{\prime}(c)=0 .$ If Rolle's Theorem cannot be applied, explain why not.
$f(x)=\frac{x^{2}-1}{x}, \quad[-1,1]$