How do you calculate the molar heat of combustion of a substance?

I'm trying to understand how to calculate the molar heat of combustion of a substance, given the heat capacity of a calorimeter as well as the mass of water that the calorimeter contains.
I cannot find any such problems online, and my book is of very little help.

Here is the example I am currently working on, and need help with:

10 g of methane (CH4) is combusted in a calorimeter that has an empty heat capacity of 18 J/°C.
The calorimeter contained 150 g of water. If the temperature changed from 25.2 °C to 30.3 °C,
calculate the molar heat of combustion of methane in J/mol.

The answer is given to me, which is -5270 J/mol. However, I am completely lost as to how I would arrive at that answer.
Please, please help!