$1 \mathrm{g}$ of a non-volatile, non-electrolyte solute of molar mass $250 \mathrm{g} {\mathrm{mol}}^{-}$ was dissolved in $51.2 \mathrm{g}$ of benzene. If the freezing point depression constant ${\mathrm{K}}_{\mathrm{f}}$ of benzene is $5.12 \mathrm{kg} \mathrm{K} {\mathrm{mol}}^{-}$, the freezing point of benzene is lowered by :