The calorific value of fuel is the amount of heat produced by the complete combustion of 1 kg of fuel.

Now,

Heat produced by 4.5 kg of fuel = 180000 kJ Therefore, heat produced by 1Kg of fuel = 180000/4.5 = 1KJ/Kg

= 40,000 kJ/kg

Hence, the calorific value of the fuel is 40,000 kJ/kg.