What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Linda is playing tennis if and only if Mary is a writer. For all y, y will play tennis if and only if y is a janitor. For all y, y is not a janitor.
If Linda plays tennis, then Mary is a writer. If Mary were a writer, then Linda is playing tennis. For all y, if y plays tennis, then y is a janitor. For all y, if y were a janitor, then y is playing tennis. For all y, y will not play tennis.