Answer
$c=-1, 0, 1$, limits $1,0,1$.
Work Step by Step
As can be seen from the figure, clearly $f(x)$ is sandwiched between $x^2$ and $x^4$ and is confined in the shaded area; based on Sandwich Theorem, we have at $c=-1, 0, 1$, $\lim\limits_{x \to -1}f(x)=1$, $\lim\limits_{x \to 0}f(x)=0$ and $\lim\limits_{x \to 1}f(x)=1$.
