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_4 -> r. t_4 -> p_4. r <-> t_4.
t_4 -> r can be inferred via the transitivity rule. r -> t_4 can be inferred via the biconditional elimination rule. t_4 -> r can be inferred via the biconditional elimination rule.