The work done per kg air in the high pressure cylinder is_____?

Question

Consider a two stage reciprocating air compressor with a perfect intercooler operating at the best intermediate pressure. Air enters the low pressure cylinder at 1 bar, 27⁰C and leaves the high pressure cylinder at 9 bar. Assume the index of compression and expansion in each stage is 1.4, and that for air R = 286.7 J/kgK. The work done per kg air in the high pressure cylinder is                                                                    

      (a) 111 kJ                                                           (b) 222 kJ

      (c) 37 kJ                                                             (d) 74 kJ