help with this, due soon!

Air containing 27.5 mole\% water vapor at an initial pressure of 1.00atm absolute is cooled in a 1.00 -liter sealed vessel from 200.0C to 15.0C Final Pressure What is the pressure in the vessel at the end of the process? (Hint: The partial pressure of air in the system can be determined from the expression pair= nairRTN and P=pair+pwater. You may neglect the volume of the liquid water condensed, but you must show that condensation occurs.) P=