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: r -> w_1. r_4 <-> w_1. ~r_4. r -> q_1. q_1 -> r.
q_1 -> w_1 can be inferred via the transitivity rule. r <-> q_1 can be inferred via the biconditional introduction rule. q_1 <-> r can be inferred via the biconditional introduction rule. r_4 -> w_1 can be inferred via the biconditional elimination rule. w_1 -> r_4 can be inferred via the biconditional elimination rule. ~w_1 can be inferred via the biconditional elimination rule.