What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? David is a janitor if and only if Elisabeth is a police officer. If David were a janitor, then it is sunny. If it is sunny, then Elisabeth is a police officer.
If David were a janitor, then Elisabeth is a police officer. If David were a janitor, then Elisabeth is a police officer. If Elisabeth were a police officer, then David is a janitor.