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_4 <-> q_15. q_1 -> w_4. ~q_15. ~r_4 -> w_4.
r_4 -> q_15 can be inferred via the biconditional elimination rule. q_15 -> r_4 can be inferred via the biconditional elimination rule. ~r_4 can be inferred via the biconditional elimination rule.