An air-water vapour mixture has a dry bulb temperature of 60°C and a
dew point temperature of 40°C. The total pressure is 101.3 kPa and the
vapour pressure of water at 40°C and 60°C are 7.30 kPa and 19.91 kPa
respectively. The humidity of air sample expressed as kg of water vapour/kg
of dry air is:
(A) 0.048
(B) 0.079
(C) 0.122
(D) 0.152