In Exercises 39-46, determine the intervals over which the function is increasing, decreasing, or constant.
$ f(x) = \left\{
\begin{array}{ll}
x+3, & \mbox{ $ x \le 0 $} \\
3, & \mbox{ $ 0 < x \le 2 $} \\
2x+1, & \mbox{ $ x > 2 $}
\end{array} \right.$