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