For the system $i-$hexane and $1-$heptene in liquid$-$vapor equilibrium at $75C$ and $1\mathrm{.}5$atm a$)$ show that it exists at only one composition in the liquid in equilibrium with the vapor. b$)$ Calculate liquid and vapor compositions.

Additional data: Antoine's equation constants when $P$ is in $mmHg$ and $T$ in $C$

$\backslash$table$[[,$A$,$B$,$C$],[$i$-$hexane,$6\mathrm{.}86839,1151\mathrm{.}401,228\mathrm{.}477],[1-$heptene,$6\mathrm{.}91381,1265\mathrm{.}120,220\mathrm{.}051]]$