Which of the following liquid pairs does not show contraction in volume on mixing?

In a mixture of components $A$ and $B$,the components show negative deviation when:

Mixing $1 \ mol$ of heptane $(V.P = 92 \ mm \ Hg)$ with $4 \ mol$ of octane $(V.P = 31 \ mm \ Hg)$ forms an ideal solution. The vapor pressure of the solution will be .......... $mm \ Hg$. (in $.2$)

For which of the following mixtures is $\Delta_{mix} H > 0$?

Liquids $A$ and $B$ form an ideal solution over the entire range of composition. At temperature $T$,an equimolar binary solution of liquids $A$ and $B$ has a vapour pressure of $45 \ Torr$. At the same temperature,a new solution of $A$ and $B$ having mole fractions $x_A$ and $x_B$,respectively,has a vapour pressure of $22.5 \ Torr$. The value of $x_A / x_B$ in the new solution is . . . . . (Given that the vapour pressure of pure liquid $A$ is $20 \ Torr$ at temperature $T$)

Which condition is not satisfied by an ideal solution?