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: p -> w. w -> p. p -> w. ~p.
~w can be inferred via the modus tollens rule. p <-> w can be inferred via the biconditional introduction rule. w <-> p can be inferred via the biconditional introduction rule. w <-> p can be inferred via the biconditional introduction rule. p <-> w can be inferred via the biconditional introduction rule.