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_19 -> p_19. q -> ~q_1. p_19 -> q_19. ~p_19. ~q_19 -> q_1.
~q_19 can be inferred via the modus tollens 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.