An adiabatic compressor is used to pressurize air from 100 kPa to 1600 kPa. If the air entering the compressor is at 300 K, and the isentropic efficiency of the air is 70 %, then calculate the required work by performing an:

(a) approximate analysis (assume 300 K values for specific heats) $\displaystyle \frac{\text{kJ}}{\text{kg}}$

(b) exact analysis (variable specific heats) $\displaystyle \frac{\text{kJ}}{\text{kg}}$