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_4. S_4(d) <-> u_4. forall z: U_1(z) -> S_4(z). forall z: S_4(z) -> U_1(z).
S_4(d) -> u_4 can be inferred via the biconditional elimination rule. u_4 -> S_4(d) can be inferred via the biconditional elimination rule. ~S_4(d) can be inferred via the biconditional elimination rule. forall z: U_1(z) <-> S_4(z) can be inferred via the universal biconditional introduction rule. forall z: S_4(z) <-> U_1(z) can be inferred via the universal biconditional introduction rule.