There are group of heat engines that work successively from the same heat source and convert it into mechanical energy. Determine group of heat engines on the basis of the PW method when the MARR is 12% per year by using the following data. Comment about your result. Investment cost Useful life Market value (EOY 15) Annual operating expenses Overhaul cost - EOY 6 Overhaul cost - EOY 8 Mechanical Energy (1000 $) 8000$ 15 years 1752$ 1168$ 292$ 420$