Let \( f(x) \) be a polynomial function such that \( f(x) + f'(x) + f''(x) = x^{5} + 64 \). Then, the value of \( \lim\limits_{x \to 1} \frac{f(x)}{x-1} \) is equal to:
\( -15 \)
\( -60 \)
\( 60 \)
\( 15 \)