Correct Answer - B
`({:("Anode :",Ag(s)toAg^+(aq)+1 e^(-)),("Cathode:",Ag^+(aq)+1e^(-)toAg):})/`
`"net":Ag_((AgBr))^+overset(1e^(-))Ag_((Ag_2CO_3))^+`
`0=0+0.059/1 log(((K_(SP)AgBr)/([Br^(-)])))/sqrt((K_(SP)Ag_2CO_3)/([CO_3^(2-)]))implies(K_(SP)AgBr)/([Br^(-)])=sqrt((K_(SP)Ag_2CO_3)/([CO_3^(2-)]))`
`implies (4xx10^(-13))/sqrt(8xx10^(-12))=([Br^(-)])/sqrt([CO_3^(-2)]) implies ([Br^(-)])/sqrt([CO_3^(-2)])=sqrt2xx10^(-7)`