An ideal-gas mixture consists of 2 kmol of N2 and 4 kmol of CO2. The apparent gas constant of the mixture is
(a) 0.215 kJ/kg = K
(b) 0.225 kJ/kg - K
(c) 0.243 kJ/kg - K
(d) 0.875 kJ/kg = K
(e) 1.24 kJ/kg - K