A mixture of methane and air is capable of being ignited only if the mole percent of methane is between 5% (lower) and 15% (upper flammability limits). A mixture containing 9.0 mole % methane in air flowing at a rate of 700 kg/h is to be diluted with pure air to reduce the methane concentration to the lower limit.(a)Calculate the required flow rate of air in mol/h.(b)Calculate the percent, by mass, of oxygen in the product gas.(c)Calculate the flow rate of an 47% methane stream that would have to be added to the original stream to prevent the the mixture from igniting.(d)Qualitatively explain why there are upper and lower flammability limits.