A very small amount of a non volatile solute (that does not dissociate) is dissolved in 56.8 cc of benzene (density 0.889 g/cc). At room temperature the vapour pressure of this solution is 98.88 mm Hg while that of benzene is 100 mmHg. 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.

5.028Kkg/mol
Hence (A) is the correct answer.