Methane combusts with air in a furnace as CH₄ + 2O₂ → CO₂ + 2H₂O. The heat of reaction ΔH_rxn = −880 kJ per mol CH₄ and is assumed to be constant. The furnace is well-insulated and no other side reactions occur. All components behave as ideal gases with a constant molar heat capacity of 44 J mol⁻¹ °C⁻¹. Air may be considered as 20 mol% O₂ and 80 mol% N₂. The air-fuel mixture enters the furnace at 50 °C. The methane conversion X varies with the air-to-methane mole ratio, r, as X = 1 − 0.1 e^{−2(r−r_s)} with 0.9 r_s ≤ r ≤ 1.1 r_s, where r_s is the stoichiometric air-to-methane mole ratio. For r = 1.05 r_s, the exit flue gas temperature in °C, rounded off to 1 decimal place, is ______