Consider a system where a Carnot engine is operating between a source and a sink. Which of the following statements about this system is/are $\text{NOT}$ correct?
- This engine is reversible.
- The engine efficiency is independent of the source and sink temperatures.
- This engine has the highest efficiency among all engines that operate between the same source and sink.
- The total entropy of this system increases at the completion of each cycle of the engine.