What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? It is sunny if and only if it is cloudy. James is writing a letter if and only if it is sunny. It is not cloudy.
If it is sunny, then it is cloudy. If James writes a letter, then it is sunny. If it is cloudy, then it is sunny. If it is sunny, then James is writing a letter. It is not sunny.