A solution contains $0.10\mathrm{M}$ each of $\mathrm{Cl}{}^{-}$ and $\mathrm{I}{}^{-}$. $\mathrm{AgNO}{}_3$ is added until $\mathrm{AgCl}$ just starts to precipitate (volume change negligible). With $K_{sp}(\mathrm{AgCl})=1.8\times 10^{-10}$ and $K_{sp}(\mathrm{AgI})=8.5\times 10^{-17}$, what percentage of the original $\mathrm{I}{}^{-}$ is still in solution at this point?

1. A$4.7\times 10^{-5}\%$
2. B$4.7\times 10^{-7}\%$
3. C$4.7\times 10^{-6}\%$
4. D$4.7\times 10^{-8}\%$