5-25) a simple, direct space heating system is currently bing used in a professional medical office complex. an upgraded "variable air volume system" retrofit can be purchased and installed for $200,000 (investment cost). Its power savings in the future will be 500,000 kilo-Watt hour. If the firm's cost of capital is 12% per year and the residual value of the system in 8 years is $20,000 should the new system be purchased? use the present worth method. (5.3)