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_2 <-> w. w -> r_1. r_1 -> t_2.
w -> t_2 can be inferred via the transitivity rule. t_2 -> w can be inferred via the biconditional elimination rule. w -> t_2 can be inferred via the biconditional elimination rule.