A mixture of methane and air is flammable only if the mole percent of methane is between 5% and 15%. A mixture containing 9 mole% methane in air flowing at 700 kg/hr is diluted with a stream of pure oxygen to reduce the methane concentration to the lower flammability limit. Calculate the required oxygen flow rate in mol/hr and the resulting mass fractions of methane and oxygen in the product stream. Air may be considered to be 21 mol% O2 and 79 mol% N2 and to have an average molecular weight of 29.0.