Helium (gas) at 25C and 4 bar is inside a glass cylinder with an internal diameter of 100 mm and a thickness of 5 mm, calculate the mass flux of helium per unit length knowing that the diffusivity is 0.396 mm^2/h, and the solubility of helium in glass is 0.45 mol/(m^3*bar). The cylinder is exposed to the environment, which is at 1 bar pressure.