Air in a piston-cylinder assembly undergoes a process from state 1, where T1= 300 K, p1= 100 kPa, to state 2 where T2=500 K, p2=650 kPa. Using the ideal gas model for air, determine the change in specific entropy between these states, in kJ/kg*K, if the process occurs
a) without irreversibilities
b) with irreversibilities