Please explain each step used solve this problem. How and why do they correct for CO?

An incineration facility burning medical waste is required to report combustion efficiency. The flue gas has the following characteristics: CO=100ppm@12%O2onadrybasisCO2=5,000ppm@7%O2onadrybasis Using the above flue gas characteristics and the EPA-required oxygen concentration on a dry basis (7%O2), the combustion efficiency is most nearly: A. 94.5% B. 97.0% C. 98.0% D. 99.9% CE=CO2+COCO2100% where CO2COCE=volumeconcentration(dry)ofCO2(partspermillion,volume;ppmv)=volumeconcentration(dry)ofCO(ppmr)=combustionefficiency Combustion efficiency (CE)=(CO2@7%)/(CO@7%+CO2@7%) Therefore, 100[(217)/(2112)]=156ppmCO corrected to 7%O2 CE=5,000/(5,000+156)=96.97% THE CORRECT ANSWER IS: B