What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? It is not sunny. James is a writer if and only if David is rich. It is sunny or Mary is excited. James is not a writer.
Mary is excited. It is not sunny and James is not a writer. James is not a writer and it is not sunny. If James were a writer, then David is rich. If David were rich, then James is a writer. David is not rich.