Chemistry help: standard heat of combustion to standard enthalpy of formation of ethanol?

Question

Ethanol undergoes combustion according to the equation

C2H5OH(l) + O2(g) ----------> CO2(g) + H2O(l)

The of ethanol, C2H5OH(l), is -1366.8 kJ/mol. Given
that:
deltaHf [CO2(g)] = -393.5 kJ/mol
deltaHf [H2O(l)] = -285.8 kJ/mol

What is the standard enthalpy of formation of ethanol ?

Thanks (ag_iitkgp)...that's what I got but don't you have to switch the -277.6 kJ/mol to +277.6 kJ/mol because we're looking for the heat of formation not the heat of combustion?

Answer 1

2*-393.5+3*-285.8+1366.8 = -277.6 kJ/mol

Answer 2

In dealing with all combustibles the atmosphere around must reach 100 % lel.