Problem $4.(25$ points$)$ Consider the beam shown in the figure below. Point $\backslash ($ A $\backslash )$ is a standard pin, and point $\backslash ($ B $\backslash )$ is a roller.

$($a$)($ Compute all reactions at points $\backslash ($ A $\backslash )$ and $\backslash ($ B $\backslash ).$

$($b$)$ Sketch $\backslash ($ V$($x$)\backslash )$ and $\backslash ($ M$($x$)\backslash ),$ marking any relevant points on the axes.