The ${\mathrm{K}}_{\mathrm{SP}}\text{ of }{\mathrm{Ag}}_2{\mathrm{CrO}}_4,\mathrm{AgCl}$, AgBr and Agl are respectively, $1.1\times {10}^{-12},1.8\times {10}^{-10},5.0\times {10}^{-13},8.3\times {10}^{-17}.$Which one of the following salts will precipitate last if AgNO₃  solution is added to the solution containing equal moles of NaCl, NaBr, Nal and Na₂CrO₄? 

$$\begin{gathered} {\mathrm{Ag}}_2{\mathrm{CrO}}_4 \\ {\mathrm{K}}_{\mathrm{sp}}={\left[{\mathrm{Ag}}^{+}\right]}^2\left[{\mathrm{Cr}}_2{\mathrm{O}}_4^{-2}\right]=1.1\times {10}^{-12} \\ \left[{\mathrm{Ag}}^{+}\right]=\sqrt{\frac{1.1\times {10}^{-12}}{\left[{\mathrm{Cr}}_2{\mathrm{O}}_4^{-2}\right]}} \\ \mathrm{AgCl} \\ {\mathrm{K}}_{\mathrm{sp}}=\left[{\mathrm{Ag}}^{+}\right]\left[{\mathrm{Cl}}^{-}\right]=1.8\times {10}^{-10} \\ \left[{\mathrm{Ag}}^{+}\right]=\frac{1.8\times {10}^{-10}}{\left[{\mathrm{Cl}}^{-}\right]} \\ \mathrm{AgBr} \\ {\mathrm{K}}_{\mathrm{sp}}=\left[{\mathrm{Ag}}^{+}\right]\left[{\mathrm{Br}}^{-}\right]=5.0\times {10}^{-13} \\ \left[{\mathrm{Ag}}^{+}\right]=\frac{5.3\times {10}^{-13}}{\left[{\mathrm{Br}}^{-}\right]} \\ \mathrm{Agl} \\ {\mathrm{K}}_{\mathrm{sp}}=\left[{\mathrm{Ag}}^{+}\right]\left[{\mathrm{I}}^{-}\right]=8.3\times {10}^{-17} \\ \left[{\mathrm{Ag}}^{+}\right]=\frac{8.3\times {10}^{-17}}{\left[{\mathrm{I}}^{-}\right]} \\ \mathrm{Ifwetake} \left[{\mathrm{Cr}}_2{\mathrm{O}}_4^{-2}\right]=\left[{\mathrm{Cl}}^{-}\right]=\left[{\mathrm{Br}}^{-}\right]=\left[{\mathrm{I}}^{-}\right]=1 \\ \mathrm{than} \mathrm{maximum} \left[{\mathrm{Ag}}^{+}\right]\mathrm{will} \mathrm{be} \mathrm{required} \mathrm{in} \mathrm{case} \mathrm{of} {\mathrm{Ag}}_2{\mathrm{CrO}}_4. \end{gathered}$$