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_6. q_6 -> q. ~q.
~q_6 can be inferred via the modus tollens rule. q <-> q_6 can be inferred via the biconditional introduction rule. q_6 <-> q can be inferred via the biconditional introduction rule.