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_11 -> s. s -> p_11. p_3 -> p_11. s -> u.
p_11 -> u can be inferred via the transitivity rule. p_3 -> s can be inferred via the transitivity rule. p_11 <-> s can be inferred via the biconditional introduction rule. s <-> p_11 can be inferred via the biconditional introduction rule.