Sulfur dioxide (SO₂) gas diffuses through a stagnant air-film of thickness 2 mm at 1 bar and 30 ℃. The diffusion coefficient of SO₂ in air is 1 × 10⁻⁵ m² s⁻¹. The SO₂ partial pressures at the opposite sides of the film are 0.15 bar and 0.05 bar. The universal gas constant is 8.314 J mol⁻¹ K⁻¹. Assuming ideal gas behavior, the steady-state flux of SO₂ in mol m⁻² s⁻¹ through the air-film is ______