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_2 <-> w. ~w. u <-> p_2. u -> p_1. p_1 -> u.
u <-> p_1 can be inferred via the biconditional introduction rule. p_1 <-> u can be inferred via the biconditional introduction rule. p_2 -> w can be inferred via the biconditional elimination rule. u -> p_2 can be inferred via the biconditional elimination rule. w -> p_2 can be inferred via the biconditional elimination rule. p_2 -> u can be inferred via the biconditional elimination rule. ~p_2 can be inferred via the biconditional elimination rule.