A solution is $0.010\mathrm{M}$ in both $\mathrm{Cl}{}^{-}$ and $\mathrm{CrO}{}_4{}^{2-}$. Solid $\mathrm{AgNO}{}_3$ is added slowly without change in volume. $K_{sp}(\mathrm{AgCl})=1.8\times 10^{-10}$, $K_{sp}(\mathrm{Ag}{}_2\mathrm{CrO}{}_4)=1.1\times 10^{-12}$. Which precipitate appears first and at what $[\mathrm{Ag}{}^{+}]$?

1. A$\mathrm{Ag}{}_2\mathrm{CrO}{}_4$, at $[\mathrm{Ag}{}^{+}]=1.1\times 10^{-10}\mathrm{M}$
2. B$\mathrm{Ag}{}_2\mathrm{CrO}{}_4$, at $[\mathrm{Ag}{}^{+}]=1.0\times 10^{-5}\mathrm{M}$
3. C$\mathrm{AgCl}$, at $[\mathrm{Ag}{}^{+}]=1.8\times 10^{-6}\mathrm{M}$
4. D$\mathrm{AgCl}$, at $[\mathrm{Ag}{}^{+}]=1.8\times 10^{-8}\mathrm{M}$