$6\mathrm{.}2\mathrm{.}34.[$Level $2]$ The lower link is moved to the right with a speed $v.r_{g_1}=4L$ and $r_{C_g}=2L.$ Determine ${}_{\frac{?}{\text{b}\text{a}\text{r}}(AB)}$ and ${}_{\frac{?}{\text{b}\text{a}\text{r}}(BC)}.$ Link $\frac{?}{\text{b}\text{a}\text{r}}(BC)$ is horizontal at this instant.

E