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 -> q_4. ~p. q_4 -> q. q -> p.
~q can be inferred via the modus tollens rule. q_4 -> p can be inferred via the transitivity rule. q <-> q_4 can be inferred via the biconditional introduction rule. q_4 <-> q can be inferred via the biconditional introduction rule.