A membrane system is used to separate a gas mixture of $50/50$ mol. C$*$O$\_\{2\}/$ C H $4,$ the permeate side is purged with $100$mL $/$ m $*$ in He$,$ the composition of C$*$O$\_\{2\}$ and C$*$H$\_\{4\}$ is analyzed with gas chromatography to determine the composition of the permeate. Membrane area is $5$c $*$ m $^2$ Membrane thickness is $2$ m$.$ Feed is at $2$ bar pressure and permeate is at $1$ bar pressure. C$*$O$\_\{2\}$ and C$*$H$\_\{4\}$ composition in the permeate is $4$ mol.$\%$ and $0\mathrm{.}02$ mol.$\%,$ respectively. Calculate the permeance and permeability of the membrane.

$($a$)$ Assume feed flow rate is high enough that feed composition can be considered as unchanged.

$($b$)$ Feed has flow rate of $100$mL $/$ m $*$ in $($at $1$ bar$).$