The composition of an ideal gas mixture, by mass, is 25% nitrogen (N2), 25% carbon dioxide (CO2) and 50% oxygen (O2). The apparent gas constant of the mixture, in kJ/kg. K, is:

(Write your answer with three decimal points; for example if the answer is 0.2876 kJ/kg. K write 0.288; if the answer is 0.2802 kJ/kg. K write 0.280; do not include the units in your answer)