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: u_3 or r. u_3 <-> u. ~u.
u_3 -> u can be inferred via the biconditional elimination rule. u -> u_3 can be inferred via the biconditional elimination rule. ~u_3 can be inferred via the biconditional elimination rule.