b$.$ Four membrane materials with the same thickness of $7\mathrm{.}6{10}^{-3}cm$ are

chosen for the natural gas sweetening process. The permeability values

of both gases are given in TABLE Q$3.$

TABLE Q$3$: Permeability data

Select the polymeric membrane which gives higher purity of $H_{2}S$

separation from $C{H}_4.$ Justify your answer.