Consider the following reference state conditions: the entropy of real saturated liquid methane at 100C is to be taken as 100 kJ/k mol K, and the entropy of hypothetical ideal gas ethane at 100C is to be taken as 200 kJ/kmol K. Calculate the entropy per kmol of a real gas mixture of 50% methane, 50% ethane (mole basis) at 20C, 4 MPa, in terms of the specified reference state values, and assuming Kay’s rule for the real mixture behavior.