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_2 -> q_6. ~q_6. p_4 <-> r_2. w_1 -> p_4.
~r_2 can be inferred via the modus tollens rule. p_4 -> r_2 can be inferred via the biconditional elimination rule. r_2 -> p_4 can be inferred via the biconditional elimination rule.