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_9. w <-> s. w or ~q_9.
q_9 -> w can be inferred via the rewriting rule. w -> s can be inferred via the biconditional elimination rule. s -> w can be inferred via the biconditional elimination rule.