\(Calorific \;Value = \frac{Heat \;Produced (in \;kJ)}{ Mass \;of\; Fuel (in \;kg)}\)
=\(\frac{180,000 k\;J}{4.5 \;kg}\)
=\(\frac{1800000}{45}\)
= \(\frac{40000 \;kJ}{kg}\)