0.1 M KI and 0.2 M ${\mathrm{AgNO}}_3$ are mixed in 3:1 volume ratio. The depression of freezing point of the resulting solution will be   $\left[{\mathrm{K}}_{\mathrm{f}}\left({\mathrm{H}}_2\mathrm{O}\right)=1.86 \mathrm{Kg} {\mathrm{mol}}^{-1}\right]$