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: t_1 -> u_3. t_1 or ~u_3. ~t_1. u_3 <-> u.
~u_3 can be inferred via the disjunctive syllogism rule. u_3 -> t_1 can be inferred via the rewriting rule. u_3 -> u can be inferred via the biconditional elimination rule. u -> u_3 can be inferred via the biconditional elimination rule.