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: q_4. t_2 -> ~q_4. s. s <-> w_1.
~t_2 can be inferred via the modus tollens rule. q_4 and s can be inferred via the conjunction rule. s and q_4 can be inferred via the conjunction rule. s -> w_1 can be inferred via the biconditional elimination rule. w_1 -> s can be inferred via the biconditional elimination rule.