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: s -> q. ~q. w <-> t_4. q -> t_4. t_4 -> s.
~s can be inferred via the modus tollens rule. s -> t_4 can be inferred via the transitivity rule. q -> s can be inferred via the transitivity rule. t_4 -> q can be inferred via the transitivity rule. w -> t_4 can be inferred via the biconditional elimination rule. t_4 -> w can be inferred via the biconditional elimination rule.