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. w <-> q_18. q or ~q_18.
q_18 -> q can be inferred via the rewriting rule. q -> w can be inferred via the biconditional elimination rule. w -> q_18 can be inferred via the biconditional elimination rule. w -> q can be inferred via the biconditional elimination rule. q_18 -> w can be inferred via the biconditional elimination rule.