Determine the change in the entropy of helium, in kJ/kg?K, as it undergoes a change of state

Question:

Determine the change in the entropy of helium, in kJ/kg?K, as it undergoes a change of state from 100 kPa and 20oC to 600 kPa and 300oC using the equation of state P(v - a) = RT where a = 0.01 m3/kg, and compare the result to the value obtained by using the ideal gas equation of state.