A gas is composed at 90% CH4 and 10% N by volume. It is burned under a boiler. The Orsat analysis of the flue gave leaving the boiler shows C0- 9.08%, O2-4.54% , N- 86.38%.Assuming the complete combustion in the furnace, the percent excess air used is: air used is: A) 22.5 B)25 C) 28 D)31.5