An automobile manufacturer determines that, on a summer day when the ambient temperature is \(311 \mathrm{~K}\), the temperature inside their new, ready-to-deliver cars reaches \(339 \mathrm{~K}\) when parked with the windows rolled up, a temperature that causes minor damage to the interiors. An engineer suggests a small in-window ventilation system. What is the maximum efficiency of an engine that operates between these two temperatures?