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 -> w_1. w_1 -> q. w_1 -> q.
q <-> w_1 can be inferred via the biconditional introduction rule. q <-> w_1 can be inferred via the biconditional introduction rule. w_1 <-> q can be inferred via the biconditional introduction rule. w_1 <-> q can be inferred via the biconditional introduction rule.