For dilute solutions containing 2.5g of a non-volatile non electrolyte solute in 100g of water,the elevation in boiling point at 1atm pressure is $4^{\large\circ}C$.Assuming concentration of solute is much lower than the concentration of solvent,the vapour pressure (mm of Hg) of the solution is (take $K_b=0.76Kkgmol^{-1})$

Question

$\begin{array}{1 1}(a)\;700\\(b)\;694\\(c)\;725\\(d)\;650\end{array}$