Compound (A) ${\mathrm{C}}_8{\mathrm{H}}_9\mathrm{Br},$ gives a white precipitate when warmed with alcoholic ${\mathrm{AgNO}}_3$ . Oxidation of (A) gives an acid (B), ${\mathrm{C}}_8{\mathrm{H}}_6{\mathrm{O}}_4$ . (B) easily forms anhydride on heating. Indentify the compound (A).