An air handling unit receives 2000 cfm of air at 60°F and 40% relative humidity. The air first passes over a heating coil that raises the temperature of the airstream to 80°F. The air then enters a humidification section where liquid water at 80°F is sprayed into the airstream. The air leaves the AHU at 80°F and 50% relative humidity. Determine: Relative humidity of the air stream after the initial heating section (before humidification).