Answer should be well explained.

Natural gas is burned to produce hot water to heat a clothing store. Assuming that the natural gas can be approximated as methane (CH4) and that the air is a simple mixture of O2 and N, in molar proportions of 1:3.76, determine the following: A. The molar air-fuel ratio for stoichiometric combustion B. The mass air-fuel ratio for stoichiometric conditions C. The operating air-fuel ratio (mass) of the heater when 4% (molar or volume) oxygen, 02, is present in the flue gases D. The percent excess air, the percent theoretical air, and the equivalence ratio associated with the conditions given in part C