Let $f(x)=\frac{(x+7{)}^2}{x^2-49}.$ Find a$)\underset{x-7}{lim}f(x),$ b$)\underset{x0}{lim}f(x),$ and c$)\underset{x7}{lim}f(x).$

a$)$ Select the correct choice below and, if necessary, fill in the answer box to complete your choice.

A$.\underset{x-7}{lim}f(x)=($Simplify your answer.$)$

B$.$ The limit does not exist.

option b is wrong