$f(x)=\{\begin{array}{cc}3x,& x4\\ x^2,& x>4\end{array}$

Find the indicated limits of $f(x),$ and determine the continuity of $f(x)$ at the indicated point. $($If the limit is i

$($a$)\underset{x{4}^{-}}{lim}f(x)$

$($b$)\underset{x{4}^{}}{lim}f(x)$

$($c$)\underset{x4}{lim}f(x)$

$($d$)$ Find $f(4).$

$($e$)f(x)$ continuous at $x=4.$