A very small amount of a non-volatile solute (that does not dissociate) is dissolved in 56.8 $c{m}^3$ of benzene (density = 0.889 g $c{m}^{-3}$). At room temperature vapour pressure of this solution is 98.88 mm Hg while that of benzene is 100mm Hg. Find the molality of this solution. If the freezing temperature of this solution is 0.73 degree lower than that of benzene, what is the value of molal freezing point depression constant of benzene? (1997-3 Marks)