What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all y_3, y_3 is a doctor if and only if y_3 will take a plane. For all y_3, y_3 is a writer if and only if y_3 will take a plane. For all y_3, if y_3 takes a plane, then y_3 is a writer. For all y_3, y_3 is not a writer.
For all y_3, y_3 will not take a plane. For all y_3, if y_3 were a doctor, then y_3 is taking a plane. For all y_3, if y_3 were a writer, then y_3 is taking a plane. For all y_3, if y_3 takes a plane, then y_3 is a doctor. For all y_3, if y_3 takes a plane, then y_3 is a writer. For all y_3, y_3 will not take a plane.