What is the relation between the vapour pressure of solution, vapour pressure of solvent and its mole fraction in the solution?

Calculate vapour pressure of a solution containing mixture of 2 moles of volatile liquid A and 3 moles of volatile liquid $B$ at room temperature. $\left(\mathrm{P}_{\mathrm{A}}^{\circ}=420, \mathrm{P}_{\mathrm{B}}^{\circ}=610 \mathrm{~mm} \mathrm{~Hg}\right.$)

Calculate the molar mass of non volatile solute when 1 g of it is dissolved in 100 g solvent decreases its freezing point by 0.2 K . $\left[\mathrm{K}_{\mathrm{f}}=1.2 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right]$

Which of the following solutions on complete dissociation exhibits maximum elevation in boiling point?