A hollow-fiber polysulfone membrane is used to separate oxygen from air for an integrated gasification power plant. A feed rate of 0.84 mol/min of air (21 mol% O2, 79 mol% N2) to a counter-flow separator produces 0.14 mol/min of permeate containing 41 mol% O2. Retentate exits the separator with 17 mol% O2. The feed and permeate pressures are 3.8 atm and 0.95 atm respectively. The polysulfone membrane has a surface area of 5.4 m and a thickness of 0.77 m. (a). What is the stage cut (%)? (b). Calculate the permeabilities of O2 and N2, in mol m/min m atm, and the membrane selectivity, 02/N2, assuming a minimal pressure drop on the feed side of the membrane, and using a log-mean average value for the feed-side composition. (c). If the membrane thickness is doubled to 1.54 m, how will this change the permeate flow rate? How will this change the membrane selectivity? Provide a short explanation with your answers (no calculations required).