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: ~w. u <-> q_2. q_2 -> u_2. u_2 <-> w.
u -> q_2 can be inferred via the biconditional elimination rule. u_2 -> w can be inferred via the biconditional elimination rule. q_2 -> u can be inferred via the biconditional elimination rule. w -> u_2 can be inferred via the biconditional elimination rule. ~u_2 can be inferred via the biconditional elimination rule.