What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all y, y is not a janitor. If David were a janitor, then Mary is a server. If it rains, then David is a janitor. If Mary were a server, then it is raining.
If David were a janitor, then it is raining. If Mary were a server, then David is a janitor.