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: u <-> r. r or q_7. u or ~q_7.
q_7 -> u can be inferred via the rewriting rule. u -> r can be inferred via the biconditional elimination rule. r -> u can be inferred via the biconditional elimination rule.