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_1 -> w_1. u <-> q_9. w_1 -> q_9.
u_1 -> q_9 can be inferred via the transitivity rule. u -> q_9 can be inferred via the biconditional elimination rule. q_9 -> u can be inferred via the biconditional elimination rule.