Which of the following statements is correct for a solution saturated with `AgCl` and `AgBr` if their solubilities in moles per litre in separate solutions are `x` and `y` respectively?
A. `[Ag^(+)]=x+y`
B. `[Ag^(+)]=[Br^(-)]+[Cl^(-)]`
C. `[Br^(-)]=y`
D. `[Cl^(-)]`