What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? u_1 -> r. forall x_17: R_17(x_17) -> S_17(x_17). ~S_17(a_17). r -> u_1. u_1 -> R_17(a_17).
r -> R_17(a_17). u_1 <-> r. r <-> u_1.