What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Richard is not a police officer. Elisabeth is playing squash. It is late if and only if Richard is a police officer.
Richard is not a police officer and Elisabeth is playing squash. Elisabeth is playing squash and Richard is not a police officer. If it is late, then Richard is a police officer. If Richard were a police officer, then it is late. It is not late.