Pure benzene, C6H6, has a molar mass of 78.114 g mol-1, a density of 0.8765 g mL-1, a freezing point of 5.45°C, and a boiling point of 80.2°C. Its freezing point depression and boiling point elevation constants are: Kf = 5.07°C m-1; Kb = 2.53oC m-1. A solution was made by taking 33.88 g of an unknown nonelectrolyte and dissolving it in 175.0 g of benzene. The measured freezing point of the solution was 1.65oC. Calculate the molar mass of the unknown substance.