Evaluate the following limits using the graph. Give an exact answer if a limit is a number. Otherwise, enter $-$ or $$ if a limit is infinite, or enter DNE if a limit does not exist in another way.

a$.\underset{x-1^{-}}{lim}f(x)=$

b$.\underset{x-1^{+}}{lim}f(x)=$

c$.\underset{x-1}{lim}f(x)=$

The graph of the $f(x)=\frac{1}{(x+1{)}^2}$ is given below. $($Click on a graph to enlarge it$.)$