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: forall x: Q(x) -> U_1(x). Q(d_4) <-> p_2. forall x: ~U_1(x). forall x: U_1(x) -> Q(x).
Q(d_4) -> p_2 can be inferred via the biconditional elimination rule. p_2 -> Q(d_4) can be inferred via the biconditional elimination rule. forall x: ~Q(x) can be inferred via the universal modus tollens rule. forall x: Q(x) <-> U_1(x) can be inferred via the universal biconditional introduction rule. forall x: U_1(x) <-> Q(x) can be inferred via the universal biconditional introduction rule.