When a 12-meter-long passenger bus is executing an overtaking maneuver on an ordinary two-lane highway, when is it safe to merge back into the original travel lane?

1. Only after the overtaken vehicle is fully visible in the interior rear-view mirror or right exterior convex mirror with at least 50 meters of clearance, signaling right in advance
2. Immediately after the front bumper passes the front wheels of the overtaken vehicle
3. As soon as the horn has been sounded twice
4. Without signaling, cutting sharply across the front of the overtaken vehicle