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_13 <-> q_13. ~u -> s. u <-> p_13. ~q_13.
p_13 -> q_13 can be inferred via the biconditional elimination rule. u -> p_13 can be inferred via the biconditional elimination rule. q_13 -> p_13 can be inferred via the biconditional elimination rule. p_13 -> u can be inferred via the biconditional elimination rule. ~p_13 can be inferred via the biconditional elimination rule.