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: p_14 -> s. s -> U(a_20). p_14 <-> r_4. forall x: U(x) -> Q_1(x).
p_14 -> U(a_20) can be inferred via the transitivity rule. p_14 -> r_4 can be inferred via the biconditional elimination rule. r_4 -> p_14 can be inferred via the biconditional elimination rule.