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. q -> t. t -> r. r -> q.
~r can be inferred via the modus tollens rule. q -> r can be inferred via the transitivity rule. t -> q can be inferred via the transitivity rule. r -> t can be inferred via the transitivity rule.