Heat Engine & Refrigerator: Practice Problem & Solution

Solution Explained:

To solve this problem, we apply the core principles of Heat Engine & Refrigerator. Understanding the underlying formula is key to arriving at the correct answer below:

The maximum possible efficiency (Carnot efficiency) is \(eta_{\text{max}} = 1 - \frac{T_L}{T_H} = 1 - \frac{300}{600} = 50\%\). Practical heat engines have efficiency less than or equal to 50%, so 50%, 35%, and 25% are all possible values.