A thin plastic membrane separates hydrogen from air. The molar concentrations of hydrogen in the membrane at the inner and outer surfaces are determined to be 0.045 and 0.002 kmol/m³, respectively. The binary diffusion coefficient of hydrogen in plastic at the operation temperature is 5.3 × 10^-10 m²/s. Determine the mass flow rate of hydrogen by diffusion through the membrane under steady conditions if the thickness of the membrane is

(a) 2 mm

(b) 0.5 mm.