= -129 kWCan someone please walk me through this?

A certain industrial process requires a steady 0.75 kg/s supply of compressed air at 500 kPa, at a maximum temperature of 30C. This air is to be supplied by installing a compressor and aftercooler. Local ambient conditions are 100 kPa, 20C. Using a reversible compressor, determine the power required to drive the compressor and the rate of heat rejection in the aftercooler.Ans: Wc = -129 kWCan someone please walk me through this?