Use the virtual work method to determine the slopes and deflections at points $B$ and $D$ of the beam shown. Can you please explain slope$($ B$,$left$)$ and slope $($B$,$right$)$IN DETAIL$$

${}_{B,\text{L}\text{e}\text{f}\text{t}}?()$

${}_{B,\text{r}\text{i}\text{g}\text{h}\text{t}}?()$

${}_D?$

${}_B?{}_D?$