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_9. q_3 or ~q_9. r <-> q_3. q_3 -> q_9.
~q_3 can be inferred via the modus tollens rule. q_9 -> q_3 can be inferred via the rewriting rule. r -> q_3 can be inferred via the biconditional elimination rule. q_3 -> r can be inferred via the biconditional elimination rule.