Determine the simple payback period of installing a heat recovery system at a cost of $1.25/cfm for a 10,000-cfm makeup air system in a laboratory located in Chicago, Illinois. The indoor temperature within the laboratory is kept at Tin = 68°F. The exhaust air temperature is Tea = 110°F. Assume that the cost of gas is $1.25/CCF and that the heat recovery system is operated 24 hours/day, 175 days/year.