The vapour pressure of pure benzene at a certain temperature is 0.850 bar. A non-volatile, non-electrolyte solid weighing 0.5 g is added to 39.0 g of benzene (molar mass 78 g mol^-1). Vapour pressure of the solution, then, is 0.845 bar. The molar mass of the solid substance is-

1. 150 g mol^–1

2. 180 g mol^–1

3. 170 g mol^–1

4. 160 g mol^–1