a mixture of methane and air is capable of being ignited only if the mole precent of methane is 5% or 15% . a mixture contaning 9.0 mole precent % of methane in air flowing at a rate 700. kg/h is to be diluted with pure air to reduce the methane concentration to the lower flammability limit . calculate the rquire flow rate of air in mol/h and the precent by mass of oxygen in the products gas. (note air may be taking to consist of 21 mole % O2 and 79 % N2 and to have an average molecular weight 29.0 .