Dilute $\mathrm{AgNO}{}_3$ solution is added dropwise to a solution containing $0.01\mathrm{M}$ each of $\mathrm{Cl}{}^{-}$ and $\mathrm{Br}{}^{-}$. Given $K_{sp}(\mathrm{AgCl})=1.8\times 10^{-10}$ and $K_{sp}(\mathrm{AgBr})=5.0\times 10^{-13}$. Which statement is correct?

1. ANeither precipitates until $[\mathrm{Ag}{}^{+}]$ reaches $0.01\mathrm{M}$
2. B$\mathrm{AgBr}$ precipitates first, because it needs a much smaller $[\mathrm{Ag}{}^{+}]$
3. CBoth precipitate together, because the anion concentrations are equal
4. D$\mathrm{AgCl}$ precipitates first, because its $K_{sp}$ is larger