Concentration of hydrogen gas across a 2mm thick palladium sheet differs by 4 kg/m3. Considering steady-state diffusion with diffusion constant 10-10 m2/s, diffusion flux is ______ kg/m2.s:

• A. 2 x 10¹⁰
• B. 2 x 10^-10
• C. 5 x 10^-11
• D. 5 x 10⁹