please do part b in GREAT detail

Question 4: A typical composition of a natural gas is 0.5% He, 17.0% N2, 76.5% CH4 and 6.0% higher hydrocarbons. The membrane proposed to separate helium has a thickness of 2.54x10 cm and the permeabilities are P'A = 60x10cm (STP).cm/(s.cm .cm Hg), P': = 3.0x100, and Pc = 1.5x10-10. It is assumed that the higher hydrocarbons are essentially non-permeable (P. 20). The feed flow rate is 2.0x109 cm (STP)/s. The feed pressure Ph = 500cmHg and the permeate pressure p = 20cmHg. a) For a fraction permeated of 0.2, calculate the permeate composition, the reject composition, and the membrane area using the complete mixing model. b) Use the permeate from part a) as feed to a completely mixed second stage. The pressure Ph = 500cmHg and p = 20cmHg. For a fraction permeated of 0.20, calculate the permeate composition and the membrane area