b and c please

105. A solution containing 4.52g of a nonelectrolyte polymer per liter of benzene solution has an osmotic pressure of 0.786 torr at 20.0C. (a) Calculate the molecular weight of the polymer. (b) Assume that the density of the dilute solution is the same as that of benzene, 0.879g/mL. What would be the freezing point depression for this solution? (c) Why are boiling point elevations and freezing point depressions difficult to use to measure molecular weights of polymers