please answer the above question (all parts)

For the problem, the system is a mall and its interior. During the day, the mall is open and temperature controlled (constant temperature), but at night the air conditioning is shut down and the mall doors are locked. (a) During the day is the system open or closed? What about at night? (Discount the movement of air when answering) (b) When would the mall be at equilibrium if at all? (c) When would the mall be at steady state if at all? (d) Answer part (b) assuming a net zero flux of people - the number of people is constant. (e) Answer part (c) assuming a net zero flux of people