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: p. q -> ~p. q -> q_3. q_3 -> q.
~q can be inferred via the modus tollens rule. q_3 -> ~p can be inferred via the transitivity rule. q <-> q_3 can be inferred via the biconditional introduction rule. q_3 <-> q can be inferred via the biconditional introduction rule.