Minimum moles of NH$_3$ required to be added to 1 L solution so as to dissolve 0.1 mol of AgCl ($K_{sp} = 1.0 \times 10^{-10}$) by the reaction is: AgCl(s) + 2NH$_3$ $\rightleftharpoons$ [Ag(NH$_3$)$_2$]$^+$ + Cl$^-$, given $K_f$ of [Ag(NH$_3$)$_2$]$^+ = 10^8$