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 <-> u. ~u. p_2 -> s. w -> p_2.
w -> s can be inferred via the transitivity rule. s -> u can be inferred via the biconditional elimination rule. u -> s can be inferred via the biconditional elimination rule. ~s can be inferred via the biconditional elimination rule.