The steam boiler is heated by fuel oil, which is assumed to contain only carbon and hydrogen. Air is supplied to the burner at $4\backslash$deg C and $0,1$ MPa. The average result of the analysis of the anhydrous fraction of the flue gas is $12,9\%$ CO$2$ by volume, $3,8\%$ O$2$ by volume and the rest N$2.$ The flue gas temperature at the base of the stack is $293\backslash$deg C and the pressure is also $0,1$ MPa.

Calculate:

a$)$ Excess air.

b$)$ The mass percentage of carbon in the fuel oil.

c$)$ The supply air consumption in m$3$ per kg of fuel oil.

d$)$ Volume of flue gas at the base of the stack in m$3$ per $1$ kg of fuel oil.