A Carnot heat engine in a factory operates at an efficiency of 0. 33 when it takes in thermal energy from a reservoir of heated water and releases thermal energy into the \(28^{\circ} \mathrm{C}\) surface water of an outdoor pool. By how much could the efficiency be improved if the thermal energy were released into the pool at a depth where the water temperature is \(18{ }^{\circ} \mathrm{C}\) ?