Two liquids $X$ and $Y$ form an ideal solution. At $300\text{K}$, vapour pressure of the solution containing $1\text{mol}$ of $X$ and $3\text{mol}$ of $Y$ is $550\text{mm Hg}$. At the same temperature, if $1\text{mol}$ of $Y$ is further added to this solution, vapour pressure of the solution increases by $10\text{mm Hg}$. Vapour pressure (in $\text{mm Hg}$) of $X$ and $Y$ in their pure states will be, respectively:

1. A
   $200$ and $300$
2. B
   $300$ and $400$
3. C
   $400$ and $600$
4. D
   $500$ and $600$