What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: ~u_1. forall x_12: P(x_12) <-> S_12(x_12). u_1 <-> r. r or ~P(h_4).
P(h_4) -> r can be inferred via the rewriting rule. u_1 -> r can be inferred via the biconditional elimination rule. r -> u_1 can be inferred via the biconditional elimination rule. ~r can be inferred via the biconditional elimination rule. forall x_12: P(x_12) -> S_12(x_12) can be inferred via the universal biconditional elimination rule. forall x_12: S_12(x_12) -> P(x_12) can be inferred via the universal biconditional elimination rule.