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: q_8 <-> q. q or w_1. w_1 <-> q_8.
q_8 -> q can be inferred via the biconditional elimination rule. w_1 -> q_8 can be inferred via the biconditional elimination rule. q -> q_8 can be inferred via the biconditional elimination rule. q_8 -> w_1 can be inferred via the biconditional elimination rule.