4. Assuming air contains 20% by volume O2 and 80% N2, for combustion of 100 standard cubic feet pe rminute (scfm) of methane (CH4) in air: CHA + 202 >

СО2 + 2 H-0 (a) The stoichiometric amount of O2 needed for a complete combustion (in scfm) (b) The stoichiometric amount of air needed for a complete combustion (in scfm) (c) The stoichiometric mixture by volume (in % methane in the stoichiometric mixture) (d) The A/F ratio (in a mass/mass ratio)