What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: Sarah is a janitor if and only if Linda is excited. Sarah is a janitor or Joseph is not reading a book.
If Joseph reads a book, then Sarah is a janitor can be inferred via the rewriting rule. If Sarah were a janitor, then Linda is excited can be inferred via the biconditional elimination rule. If Linda were excited, then Sarah is a janitor can be inferred via the biconditional elimination rule.