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: s <-> q_7. u or ~q_7. ~t_2. u -> t_2.
~u can be inferred via the modus tollens rule. q_7 -> u can be inferred via the rewriting rule. s -> q_7 can be inferred via the biconditional elimination rule. q_7 -> s can be inferred via the biconditional elimination rule.