Q$3$: A power plant using a thermodynamic cycle with a thermal efficiency of $41\%$ produces $700$ million kWh per year of electricity; the fuel is natural gas. If the electric generator is $98\%$ efficient, the combustor is $88\%$ efficient, and gas costs $$8/$GJ$,$ calcul$$te:

The total gas energy content required per year, in GJ;

The annual expenditure on gas, in $;

The mass of $C{O}_2$ emitted per year from the plant, in kg ; gas provides energy at a rate of $18\mathrm{.}2M\frac{J}{k}gC{O}_2$ emitted.