A mixture of CO₂ and CH₄ is separated by a cellulose acetate membrane at 35°C. The permeability of CO₂ and CH₄ are 15.0 x 10^-10 and 0.48 x 10^-10 cm³ (STP) cm/cm² s cm Hg, respectively. Thus, the selectivity, α_CO2-CH4 = 31. The high (retentate side) and low (permeate side) pressures are 20.0 and 1.1 atm, respectively. The simulation plots (1) the RT curve, which relates CO₂ mole fractions on both sides of the membrane, and (2) the operating line, whose slope depends on the stage cut, θ. Assuming that both retentate and permeate sides are well mixed, the graphical solution of this gas permeation problem is given by the intersection point shown in cyan in the figure. You can set the feed composition and the stage cut.