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 or ~q_7. t <-> u. ~t.
q_7 -> u can be inferred via the rewriting rule. t -> u can be inferred via the biconditional elimination rule. u -> t can be inferred via the biconditional elimination rule. ~u can be inferred via the biconditional elimination rule.