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_2 <-> q_11. w_2 -> q_11. q_11 -> w_2.
w_2 <-> q_11 can be inferred via the biconditional introduction rule. q_11 <-> w_2 can be inferred via the biconditional introduction rule. w_2 -> q_11 can be inferred via the biconditional elimination rule. q_11 -> w_2 can be inferred via the biconditional elimination rule.