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 <-> p. u_4 <-> w. ~u_4.
w -> p can be inferred via the biconditional elimination rule. u_4 -> w can be inferred via the biconditional elimination rule. p -> w can be inferred via the biconditional elimination rule. w -> u_4 can be inferred via the biconditional elimination rule. ~w can be inferred via the biconditional elimination rule.