What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? s_1 -> p_1. t -> s_1. p_1 -> r_15. p_12 <-> r_15. ~p_12.
s_1 -> r_15. p_12 -> r_15. r_15 -> p_12. ~r_15.