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: There is at least one y for which y is a doctor. For all y, y is a politician and y is an astronaut. For all y, if y were a doctor, then y is a janitor.
There is at least one y for which y is a janitor can be inferred via the existential modus ponens rule. For all y, y is a politician can be inferred via the universal simplification rule. For all y, y is an astronaut can be inferred via the universal simplification rule.