Air entering at 70F and atmospheric pressure is to be compressed to 4,000 lb /in. 2

Air entering at 70°F and atmospheric pressure is to be compressed to 4,000 lb_ƒ/in.² gauge in a reciprocating compressor at the rate of 125 std ft³/min. If the compression ratio is the same in each stage, how many stages should be used? What is the theoretical shaft work per standard cubic foot for frictionless adiabatic compression? What is the brake horsepower if the efficiency of each stage is 85 percent? For air, γ = 1.40.