What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? ~s. s <-> t. forall x_15: R_15(x_15) -> S_15(x_15). t <-> S_15(a_15).
s -> t. t -> S_15(a_15). t -> s. S_15(a_15) -> t. ~t.