I re-posted it so a real expert can answer), these questions have long solutions.

A natural gas fumace is being used to heat steam to drive a turbine for power generation. You can estimate the composition of the natural gas as 94 mole% methane and 6 mole% ethane. This is burned using 20% excess air supplied at 25 C and 1 atm absolute. The furnace achieves a fractional conversion of methane of 0.9 and complete conversion of ethane. Of the methane converted 10% undergoes incomplete combustion (the remainder complete combustion) and all of the ethane undergoes complete combustion. Use a basis of 100 moles natural gas feed per hour. (a) (10 points) What is the volumetric flow rate of air needed for the fumace if the inlet air as supplied has a relative humidity of 40%