$4.)$ Parts a$)$ and b$)$ should be calculated using equations. Part c$)$ should utilize the psychrometric chart.

a$)$ Air in a $3000m^3$ room is maintained at $20C$ and $50\%$ humidity at a high elevation where the atmospheric pressure is $80$ kPa $.$ What is the humidity ratio?

b$)$ If the humidity ratio from the room in part a$)$ is reduced to $0\mathrm{.}015k\frac{g}{k}{g}_w$ while maintaining the temperature, what is the mass of water in the air?

c$)$ Air at $0C$ and $80\%$ humidity is heated to $25C.$ It no water is added to the air, what is the new relative humidity?