The volume and temperature of air (assumed to be an ideal gas) in a closed vessel is 2.87m3 and 300 K, respectively. The gauge pressure indicated by a manometer fitted to the wall of the vessel is 0.5 bar. If the gas constant of air is R = 287 J/kg K and the atmospheric pressure is 1 bar, the mass of air (in kg) in the vessel is
1. 1.67
2. 3.33
3. 5.00
4. 6.66