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 <-> u_1. q. ~u_1.
q and ~u_1 can be inferred via the conjunction rule. ~u_1 and q can be inferred via the conjunction rule. u -> u_1 can be inferred via the biconditional elimination rule. u_1 -> u can be inferred via the biconditional elimination rule. ~u can be inferred via the biconditional elimination rule.