problem $2(10$ points$).$ A binary mixture consists of $50\mathrm{.}7$mol$\%$ n$-$butane $(1)$ and the balance iso$-$butane $(2).$ Using Raoult's Law:

a$)$ Estimate the bubble point pressure at $71C$ and calculate the composition of the first bubble of vapor.

b$)$ Estimate the dew point pressure at $71C,$ and the composition of the first drop of liquid.

c$)$ Comment on whether the use of Raoult's Law is justifiable for this system, why or why not? Explain clearly but briefly.