Air is heated in an adiabatic piston cylinder device at a constant pressure of 100 kPa. The initial specific volume of air is 1 m3/kg. If the volume of the cylinder is increased by 50% in this process, determine the specific entropy change of air in kJ/kg.K, Assuming:
a. Constant specific heat.
b. Variable specific heat.
(Assume for both, ideal gas behavior for air and average cP = 1.005 kJ/kg.K)