What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? forall x: P(x) <-> U(x). ~P(f_2). u <-> U(f_2).
u -> U(f_2). U(f_2) -> u. forall x: P(x) -> U(x). forall x: U(x) -> P(x).