Consider the function \( f(x)=\frac{x^{2}-49}{x(x-7)} \).
a. Evaluate \( \lim _{x \rightarrow \infty} f(x) \) and \( \lim _{x \rightarrow-\infty} f(x) \), and then identify the horizontal asymptotes.
b. Find the vertical asymptotes. For each vertical asymptote \( x=a \), evaluate \( \lim _{x \rightarrow a^{-}} f(x) \) and \( \lim _{x \rightarrow a^{+}} f(x) \).
a. Evaluate \( \lim _{x \rightarrow \infty} f(x) \). Select the correct choice and, if necessary, fill in the answer box to complete your choice.
A. \( \lim _{x \rightarrow \infty} \frac{x^{2}-49}{x(x-7)}=\square \) (Simplify your answer.)
B. The limit does not exist and is neither \( -\infty \) nor \( \infty \).