Calculating Heat Release from Bomb calorimeter
Heat of combustion is the amount of heat (enthalpy) liberated when 1 mole $\ce{CH4}$ reacts (combusts) with oxygen.

In other words, what is the heat of reaction in this case?

$\ce{CH4(g) + 2O2(g) -&gt; CO2(g) + 2H2O(l)}$

Then you must ask yourself, what happens after the heat is produced i.e. where does it go? It quickly turns into an accounting problem...

Take a look at: Constant Volume Calorimetry