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: p_9 -> u_1. p_9 <-> q. u_1 -> q.
p_9 -> q can be inferred via the transitivity rule. p_9 -> q can be inferred via the biconditional elimination rule. q -> p_9 can be inferred via the biconditional elimination rule.