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 <-> s_2. w <-> r. r -> t. s_2 or w.
t -> s_2 can be inferred via the biconditional elimination rule. w -> r can be inferred via the biconditional elimination rule. s_2 -> t can be inferred via the biconditional elimination rule. r -> w can be inferred via the biconditional elimination rule.