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: w -> p_4. w <-> q_9. p_4 -> q_9.
w -> q_9 can be inferred via the transitivity rule. w -> q_9 can be inferred via the biconditional elimination rule. q_9 -> w can be inferred via the biconditional elimination rule.