What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? There is at least one y_4 for which if y_4 were a doctor, then y_4 is sleeping. For all y_4, y_4 is a doctor or y_4 will not sleep.
For all y_4, if y_4 sleeps, then y_4 is a doctor.