Estimation of Halogen Percentage by the Carius Method

What is the molar mass of silver bromide ($\mathrm{A}\mathrm{g}\mathrm{B}\mathrm{r}$) using the given relative atomic masses of $\mathrm{A}\mathrm{g}$ ($108\mathrm{u}$) and $\mathrm{B}\mathrm{r}$ ($80\mathrm{u}$)?

Which expression correctly relates the mass of bromine in the precipitate to the mass of $\mathrm{A}\mathrm{g}\mathrm{B}\mathrm{r}$ obtained?

What is the percentage of bromine in the organic compound, given by $\frac{\text{mass of }\mathrm{B}\mathrm{r}}{\text{mass of compound}}\times 100$, rounded to the nearest integer?