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_4 -> r. ~q_6. q_4 <-> q_6. q_4 -> r. r -> q_4.
q_4 <-> r can be inferred via the biconditional introduction rule. q_4 <-> r can be inferred via the biconditional introduction rule. r <-> q_4 can be inferred via the biconditional introduction rule. r <-> q_4 can be inferred via the biconditional introduction rule. q_4 -> q_6 can be inferred via the biconditional elimination rule. q_6 -> q_4 can be inferred via the biconditional elimination rule. ~q_4 can be inferred via the biconditional elimination rule.