A mixture of methane and air has capability of being ignited if mole percent of methane is between 5 and 15%. A mixture containing 9.0 mole% methane in air flowing at a rate of 700. kg/hr is to be diluted with pure air to reduce the methane concentration to the lower flammability limit. Calculate the required flow rate of air in mol/hr and the percent by mass of oxygen in the product gas. Air may be taken to consist of 21 mole% O2, and 79% N2 and to have an average molecular weight of 29.0.