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_11 -> w_4. w_4 -> p_11. p_11 <-> r.
p_11 <-> w_4 can be inferred via the biconditional introduction rule. w_4 <-> p_11 can be inferred via the biconditional introduction rule. p_11 -> r can be inferred via the biconditional elimination rule. r -> p_11 can be inferred via the biconditional elimination rule.