<s>[INST] If we depended on the sun for all our energy, we'd be using about 10 to the 16th power per year. If we were to get this much energy from a finite source, we need to look into what that would take.
As an initial estimate, assume fossil fuels contain 40 megajoules of energy per kilogram. This is a rough estimate, but it will have to do.
Now if we need 10 to the 16th power joules, and each kilogram of fossil fuel contains 40 megajoules of energy, how many kilograms of fossil fuels would we need?[/INST]