An air water vapor mixture has a DBT of 60°C and a DPT of 40° C. The WBT (Tw) for the above mixture would be

• For the unsaturated air-vapour mixture:
Dry bulb temperature > Wet bulb temperature > Dew point temperature
​Hence the relation for air-water vapour mixture has a DBT of 60°C and a DPT of 40°C, 40°C < TW < 60°C
For the saturated air-vapour mixture:​​​
Dry bulb temperature = Wet bulb temperature = Dew point temperature (Because Dew point depression = 0)

🔴Additional Information:
Dry Bulb Temperature (DBT): The temperature of the air measured by an ordinary thermometer.
Wet Bulb Temperature (WBT): The temperature measured by the thermometer when its bulb is covered with a wet cloth and is exposed to a current of moving air.
Dew Point Temperature (DPT): The temperature at which condensation starts, is known as the dew point temperature.  
Dew Point Depression (DPD): The difference between DBT and DPT is known as dew point depression