Let $f$ be defined by

$f(x)=\{\begin{array}{cc}7x+m,& x<mn>2</mn>\\ -7x^2+2m,& x2\end{array}$

$($a$)$ Find $($in terms of $m)$: $\underset{x{2}^{+}}{lim}f(x)=$

$($b$)$ Find $($in terms of $m)$: $\underset{x{2}^{-}}{lim}f(x)=$

$($c$)$ Find all values of $m$ such that

$\underset{x{2}^{-}}{lim}f(x)=\underset{x{2}^{+}}{lim}f(x)$

$($Note: if there are more than one such value, list them separated by commas$)$

Values of $m=$