A mixture with a $60$:$40$ molar ratio of $1-$hexene and i$-$hexane is contained in a

sealed vessel. Initially the mixture is entirely a liquid at a very high pressure and

a temperature of $25$C$.$ While maintaining the temperature constant at $25$C$,$ the

system pressure is steadily decreased. Clearly stating all assumptions, please

calculate the approximate values of:

a$.$ The pressure when the first bubble of vapour is formed.

b$.$ The composition of the first bubble of vapour.

c$.$ The pressure at which the last drop of liquid is vaporized.

d$.$ The composition of the last drop of liquid