$(25\%)$ Q$1.$ A semipermeable membrane is used for the partial removal of oxygen from air that is blown through a grain elevator storage facility. Ambient air $(79\%$ nitrogen, $21\%$ oxygen on a mole basis$)$ is compressed to an appropriate pressure, cooled to ambient temperature $25C,$ and then fed through a bundle of hollow polymer fibers that selectively absorb oxygen, so the mixture leaving at $120$kPa,$25C,$ contains only $5\%$ oxygen, shown in Fig. Q$1.$ The absorbed oxygen is bled off through the fiber walls at $40$kPa,$25C,$ to a vacuum pump. Assume the process to be reversible and adiabatic and determine the minimum inlet air pressure to the fiber bundle.