A stream of outdoor air is mixed with a stream of return air in an air conditioning system that operates at 101 kPa pressure. The flow rate of outdoor air is 3 kg/s, and its condition is 30 degrees Celsius Tdb and 23 degrees Celsius Twb. The flow rate of return air is 2.5 kg/s and its condition is 15 degrees Celsius Twb and 60% RH. Determine the dry bulb temperature of the mixture, and the dry bulb temperature by the weighted average of the dry bulb temperatures of the entering streams.