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: q -> u. w_3 <-> u. w_3 -> q.
w_3 -> u can be inferred via the transitivity rule. w_3 -> u can be inferred via the biconditional elimination rule. u -> w_3 can be inferred via the biconditional elimination rule.