Methane (CH_{4}, M = 16.04 kg/kmol) is burned in a gas engine with 125 % theoretical air. Stoichiometric equation: CH_{4} + 2(O_{2} + 3.76N_{2}) → CO_{2} + 2H_{2}O + 7.52N_{2}; M_{air} = 28.97 kg/kmol. Find the air–fuel ratio by mass (answer in kg/kg).