What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? s -> R_20(b). r_4 -> s. r_4 <-> u_3. forall x_20: R_20(x_20) -> S_20(x_20).
r_4 -> R_20(b). r_4 -> u_3. u_3 -> r_4.