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: ~r_1. p_3 or q_4. r_1 <-> u_1. ~p_3.
q_4 can be inferred via the disjunctive syllogism rule. ~r_1 and ~p_3 can be inferred via the conjunction rule. ~p_3 and ~r_1 can be inferred via the conjunction rule. r_1 -> u_1 can be inferred via the biconditional elimination rule. u_1 -> r_1 can be inferred via the biconditional elimination rule. ~u_1 can be inferred via the biconditional elimination rule.