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 -> ~s_1. s_1. p_19 <-> t_3. ~t_3. t <-> q_4.
~q_4 can be inferred via the modus tollens rule. s_1 and ~t_3 can be inferred via the conjunction rule. ~t_3 and s_1 can be inferred via the conjunction rule. p_19 -> t_3 can be inferred via the biconditional elimination rule. t -> q_4 can be inferred via the biconditional elimination rule. t_3 -> p_19 can be inferred via the biconditional elimination rule. q_4 -> t can be inferred via the biconditional elimination rule. ~p_19 can be inferred via the biconditional elimination rule.