2. (30) Stale air on airplanes It is thought that people develop respiratory infections during air travel because much of the airplane cabin air is recirculated. Airlines claim that using only fresh air in the cabin is too costly since at an altitude of 30,000ft, the outside conditions are 50oC and 0.1bar, requiring air to be compressed and heated before being introduced into the cabin. A typical airplane cabin has a volume of 100m3 with air at in-flight conditions of 0.8 bar and 25oC. Estimate the cost of completely refreshing the air every minute if energy costs $0.2/kWh, and calculate the change in the entropy of the universe in time, using a. (10) A reversible adiabatic compressor followed by an isobaric heat exchanger b. (10) An adiabatic compressor with 80% efficiency followed by an isobaric heat exchanger c. (10) The most efficient process possible