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 <-> w_2. s -> q. q -> r_6.
s -> r_6 can be inferred via the transitivity rule. s -> w_2 can be inferred via the biconditional elimination rule. w_2 -> s can be inferred via the biconditional elimination rule.