For a dilute solution containing 2.5 g of a non- volatile non- electrolyte solute in 100 g of water, the elevation in boiling point at 1 atm pressure is $2^{\circ} \mathrm{C}$. Assuming concentration of solute is much lower than the concentration of solvent, the vapour pressure (mm of Hg) of the solution is (take $\mathrm{K}_{\mathrm{b}}=0.76 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$ )