The air with enthalpy of 100 KJ/kg is compressed by an air compressor to a pressure and temperature at which its enthalpy becomes 200 kJ/jg. The loss of heat is 40 kJ/kg form the compressor as the air passes through it. Neglecting kinetic and potential energies the power required for an air mass flow of 0.5 kJ/s is
(a) 30kW (b) 50 kW
(c)70 kW (D) 90 kW