Vapour pressures of pure liquids $A$ and $B$ are $300$ and $800 \ torr$ respectively at $25^{\circ}C$. When these two liquids are mixed at this temperature to form a solution in which mole percentage of $B$ is $90$,the total vapour pressure is observed to be $720 \ torr$. Which of the following is true for this solution?

• A
  $\Delta V_{\text{mix}} > 0$
• B
  $\Delta H_{\text{mix}} < 0$
• C
  $\Delta V_{\text{mix}} = 0$
• D
  $\Delta S_{\text{mix}} < 0$