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: For all y, if y were a doctor, then y is fast. There is at least one y for which y is not fast. For all y, if y were a janitor, then y is a doctor. For all y, if y were fast, then y is a janitor.
There is at least one y for which y is not a doctor can be inferred via the existential modus tollens rule. For all y, if y were a doctor, then y is a janitor can be inferred via the universal transitivity rule. For all y, if y were a janitor, then y is fast can be inferred via the universal transitivity rule. For all y, if y were fast, then y is a doctor can be inferred via the universal transitivity rule.