The decrease in available energy is calculated using the formula:
\( \Delta Q = \dot{Q} \left( 1 - \frac{T_2}{T_1} \right) \)
Where: \( \dot{Q} = 7200 \, \text{kJ/min}, \, T_1 = 1000 \, K, \, \text{and} \, T_2 = 300 \, K \). After plugging in the values:
\( \Delta Q = 7200 \times \left( 1 - \frac{300}{1000} \right) = 7200 \times 0.7 = 5040 \, \text{kJ/min} \)