1. The problem statement, all variables and given/known data It is thought that people develop respiratory infections during air travel because much of the airplane cabin air is recirculated. Airiines claim that using orlly fresh air in the cabins is too costly since at an altitude of 30 000 feet the outside conditions are -50°C and 0.1 bar, so that the air would have to be compressed and heated before being introduced into the cabin. The air- plane cabin has a volume of 100 m3 with air at the in- flight conditions of 25°C and 0.8 bar. What would be the cost of completely refreshing the air every minute if air has a heat capacity of Cp; = 30 J/(mol K) and energy costs,$0.2 per kW hr? 2. Relevant equations Energy Balance 3. The attempt at a solution So far I've simply used Q/ΔT=Cp to find the heat. But I'm not sure what to do or what formulas would be applicable from this point.