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 <-> q_11. ~q_11. p_11 -> q_11. u_1 <-> p_11.
~p_11 can be inferred via the modus tollens rule. p_11 -> q_11 can be inferred via the biconditional elimination rule. u_1 -> p_11 can be inferred via the biconditional elimination rule. q_11 -> p_11 can be inferred via the biconditional elimination rule. p_11 -> u_1 can be inferred via the biconditional elimination rule. ~p_11 can be inferred via the biconditional elimination rule.