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: s_2 -> w_2. w_2 -> s_2. s_2 -> s.
w_2 -> s can be inferred via the transitivity rule. s_2 <-> w_2 can be inferred via the biconditional introduction rule. w_2 <-> s_2 can be inferred via the biconditional introduction rule.