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: w <-> s. ~p_12. p_12 <-> s.
w -> s can be inferred via the biconditional elimination rule. p_12 -> s can be inferred via the biconditional elimination rule. s -> w can be inferred via the biconditional elimination rule. s -> p_12 can be inferred via the biconditional elimination rule. ~s can be inferred via the biconditional elimination rule.