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: exists x_5: U_4(x_5) -> R_4(x_5). forall x_5: U_4(x_5) -> ~Q(x_5). forall x_5: R_4(x_5) -> U_4(x_5). forall x_5: Q(x_5).
forall x_5: ~U_4(x_5) can be inferred via the universal modus tollens rule. exists x_5: U_4(x_5) <-> R_4(x_5) can be inferred via the existential biconditional introduction rule. exists x_5: R_4(x_5) <-> U_4(x_5) can be inferred via the existential biconditional introduction rule.