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. s <-> t. p_15 -> r_15. w_1 -> r_15. p_15 or w_1.
r_15 can be inferred via the disjunction elimination rule. s -> t can be inferred via the biconditional elimination rule. t -> s can be inferred via the biconditional elimination rule. ~t can be inferred via the biconditional elimination rule.