80 mole percent of $\mathrm{MgCl}_{2}$ is dissociated in aqueous solution. The vapour pressure of $1.0 ~\mathrm{molal}$ aqueous solution of $\mathrm{MgCl}_{2}$ at $38^{\circ} \mathrm{C}$ is ____________ $\mathrm{mm} ~\mathrm{Hg.} ~\mathrm{(Nearest} ~\mathrm{integer)}$

Given : Vapour pressure of water at $38^{\circ} \mathrm{C}$ is $50 \mathrm{~mm} ~\mathrm{Hg}$