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_15 -> w. w -> p_15. ~p_15. w <-> q_7.
~w can be inferred via the modus tollens rule. p_15 <-> w can be inferred via the biconditional introduction rule. w <-> p_15 can be inferred via the biconditional introduction rule. w -> q_7 can be inferred via the biconditional elimination rule. q_7 -> w can be inferred via the biconditional elimination rule.