An HVAC unit maintains air at 75F dry-bulb temperature and 50% relative humidity. Outside air is supplied to the system at 3000 ft3/min at 91F dry-bulb and 77F wet-bulb. The flow of the return air through the system is 7000 ft3/min. The supply air leaves the air conditioner with an enthalpy of 22 Btu/lbm. The system utilizes an energy recovery ventilator with an effectiveness of 75% for the outside airstream exhaust to condition the fresh 3000 ft3/min incoming airstream before it mixes with the 7000 ft3/min of return air. Assume the supply and exhaust specific heats are approximately equal, and assume the specific volume of the air is approximately constant at 13.33 ft3/lbm across the states. The resulting cooling load is most nearly 

Answers 310,500 Btu/hr 390,000 Btu/hr 400,000 Btu/hr 454,000 Btu/hr