Liquid $\text{'}M\text{'}$ and liquid 'N' form an ideal solution. The vapour pressures of pure liquids 'M' and $\text{'}N\text{'}$are $450$and $700 mmHg$, respectively, at the same temperature. Then correct statement is

$X_M$ = Mole fraction of $\text{'}M\text{'}$ in solution ;

$X_N$ = Mole fraction of $\text{'}N\text{'}$ in solution ; 

$Y_M$ = Mole fraction of $\text{'}M\text{'}$ in vapour phase ; 

$Y_N$ = Mole fraction of $\text{'}N\text{'}$ in vapour phase)