Let f(x) be a polynomial of degree 6 in x, in which the coefficient of x^6 is unity and it has extrema at x=-1 and x=1. If lim_x → 0 (f(x))/x^3=1,…

Let $\displaystyle f(x)$ be a polynomial of degree $\displaystyle 6$ in $\displaystyle x$, in which the coefficient of $\displaystyle x^6$ is unity and it has extrema at $\displaystyle x=-1$ and $\displaystyle x=1$. If $\displaystyle \lim _{x \rightarrow 0} \frac{f(x)}{x^3}=1$, then $\displaystyle 5 \cdot f(2)$ is equal to \_\_\_\_.