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_3. p_3 <-> u. u -> q_11. q_11 -> u.
u <-> q_11 can be inferred via the biconditional introduction rule. q_11 <-> u can be inferred via the biconditional introduction rule. p_3 -> u can be inferred via the biconditional elimination rule. u -> p_3 can be inferred via the biconditional elimination rule. ~u can be inferred via the biconditional elimination rule.