Evaluate the following limits. If needed, enter inf for $\infty$ and -inf $-\infty$.

(a) $\displaystyle\lim_{x \rightarrow \infty} x^2(-7 + 3 x)(6 - 7 x ) =$

(b) $\displaystyle \lim_{x \rightarrow -\infty} x^2(-7 + 3 x )(6 -7 x) =$