Let \( f(x) \) be a polynomial of degree \( 5 \), and have extrema at \( x=1 \) and \( x=-1 \). If \( \displaystyle \lim_{x\to0}\left(\dfrac{f(x)}{x^{3}}\right)=-5 \), then \( f(2)-f(-2) \) is equal to:
\( 0 \)
\( 50 \)
\( 92 \)
\( 112 \)