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 <-> q_8. w or q_4. q_8 -> r_1. q_4 -> r_1.
w -> q_8 can be inferred via the biconditional elimination rule. q_8 -> w can be inferred via the biconditional elimination rule.