$($a$)(10$ points$)$ Calculate mass fraction of propylene in a gas mixture containing $80\%$ propylene and

the balance nitrogen $($by mole$)$ at $400C$ and $2$ bar.

$($b$)(15$ points$)$ Calculate specific enthalpy $($in $k\frac{J}{k}g)$ of the gas mixture relative to pure components

at $25$ and $1$atm. State the assumptions you made in doing the calculation.