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: t_4 -> t. t -> w. w -> t_4. t_4 -> w.
t_4 -> w can be inferred via the transitivity rule. t -> t_4 can be inferred via the transitivity rule. w -> t can be inferred via the transitivity rule. w <-> t_4 can be inferred via the biconditional introduction rule. t_4 <-> w can be inferred via the biconditional introduction rule.