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: t_3 -> q. ~q_19. q_19 -> p_19. p_19 -> q_19. ~q.
~t_3 can be inferred via the modus tollens rule. ~p_19 can be inferred via the modus tollens rule. ~q_19 and ~q can be inferred via the conjunction rule. ~q and ~q_19 can be inferred via the conjunction rule. q_19 <-> p_19 can be inferred via the biconditional introduction rule. p_19 <-> q_19 can be inferred via the biconditional introduction rule.