In a Heating System, Cold Outdoor Air at 10°C Flowing

In a heating system, cold outdoor air at 10°C flowing at a rate of 6 kg/min is mixed adiabatically with hot air at 50°C flowing at a rate of 1.5 kg/min. Assuming constant specific heats at room temperature, the exit temperature of the mixture is

A) 30°C
B) 18°C
C) 45°C
D) 22°C
E) 38°C