On dissolving 0.5 g of a non-volatile non-ionic solute to 39 g of benzene, its vapor pressure decreases from 650 mm Hg to 640 mm Hg. The depression of freezing point of Benzene (in K) upon addition of the solute is_____(Given data : Molar mass and the molal freezing point depression constant of benzene are 78 g mol-1 and 5.12 K.kg  mol-1, respectively)