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_7 or ~u. p_7 <-> u.
u -> p_7 can be inferred via the rewriting rule. p_7 -> u can be inferred via the biconditional elimination rule. u -> p_7 can be inferred via the biconditional elimination rule.