A two-stage air compressor consists of three cylinders having the same bore and stroke. The delivery pressure is 7 bar and the FAD is 4.2 m3 /min. Air is drawn in at 1.013 bar, 15 C and an intercooler cools the air at 38 C. The index of compression is 1.3 for all three cylinders. Neglecting clearance, calculate: (i) the intermediate pressure; (ii) the power required to drive the compressor; (iii) The isothermal efficiency.