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_1 -> r_4. ~r. r_4 -> w_4. w_4 -> r_1. r <-> r_4.
r_1 -> w_4 can be inferred via the transitivity rule. r_4 -> r_1 can be inferred via the transitivity rule. w_4 -> r_4 can be inferred via the transitivity rule. r -> r_4 can be inferred via the biconditional elimination rule. r_4 -> r can be inferred via the biconditional elimination rule. ~r_4 can be inferred via the biconditional elimination rule.