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 writes a letter, then y is driving a car. For all y, if y were a doctor, then y is a janitor. There is at least one y for which if y drives a car, then y is a janitor. For all y, y is a carpenter or y will write a letter. For all y, y is not a carpenter or y is a doctor.
There is at least one y for which if y writes a letter, then y is a janitor can be inferred via the existential transitivity rule. For all y, y will write a letter or y is a doctor can be inferred via the universal resolution rule.