Question $5(6$ marks$)$

The pressure in a pipeline that transports helium gas is maintained at $14\mathrm{.}5$ psia by venting helium to the atmosphere through a $0\mathrm{.}4-$in$-$internal$-$diameter tube that extends $30ft$ into the air. Assuming both the helium and the atmospheric air to be at $80F,$ the concentrations of species in the pipeline and the atmosphere remain constant. Assume helium and air are ideal the pipeline and helium concentration in the atmosp diffusion process. Determ $D_{AB}=7\mathrm{.}75{10}^{-4}f\frac{t^2}{s}.$ You can consider this process as equimolar counter atmosphere through the tube $($a$)$ the mass flow rate $(1b\frac{m}{s}$ of helium lost to the into the pine $(2$ mark$)($b$)$ the mass flow rate $(lb\frac{m}{s})$ of air that infiltrates into the pipeline $(2$ mark$)$