Air at 40C and 20 % relative humidity at a barometric pressure of 101,32 kPa, flows with an average velocity of 4 m/s in a square duct with dimensions 500 x 500 mm. Air at 30C and 60 % relative humidity, also at 101,325 kPa, flows with the same velocity in another square duct with dimensions of 400 x 400 mm. If both ducts converge into one, calculate or determine: 1.1 the mixed air temperature using both volume and mass flow rates and show that there is negligible difference in the answers; 1.2 the relative humidity of the mixture ; and 1.3 the dimensions of a square duct conveying the mixed air if the average velocity of the mixed air stream is to be maintained at 4 m/s.