For a gas the mole fractions are: CH_{4} 94.5 %, C_{2}H_{6} 0.8 %, C_{3}H_{8} 0.4 %, CO_{2} 0.3 %, N_{2} 4 %. Find the molecular weight of the gas in kg/kmol (take M = 16, 30, 44, 44 and 28 kg/kmol respectively).