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_13: Q_13(x_13) -> U(x_13). forall x_13: U(x_13) -> Q_13(x_13). p_8 <-> Q_13(a_12). ~p_8.
p_8 -> Q_13(a_12) can be inferred via the biconditional elimination rule. Q_13(a_12) -> p_8 can be inferred via the biconditional elimination rule. ~Q_13(a_12) can be inferred via the biconditional elimination rule. forall x_13: Q_13(x_13) <-> U(x_13) can be inferred via the universal biconditional introduction rule. forall x_13: U(x_13) <-> Q_13(x_13) can be inferred via the universal biconditional introduction rule.