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: Jennifer is not a sailor. If Barbara were a janitor, then Joseph is playing squash. If Joseph plays squash, then Barbara is a janitor. Jennifer is a politician if and only if Joseph is playing squash. If Jennifer were a politician, then Jennifer is a sailor.
Jennifer is not a politician can be inferred via the modus tollens rule. Barbara is a janitor if and only if Joseph is playing squash can be inferred via the biconditional introduction rule. Joseph is playing squash if and only if Barbara is a janitor can be inferred via the biconditional introduction rule. If Jennifer were a politician, then Joseph is playing squash can be inferred via the biconditional elimination rule. If Joseph plays squash, then Jennifer is a politician can be inferred via the biconditional elimination rule.