At what point after passing a vehicle is it safe to move back into the right-hand lane?

• You can see the left-hand headlight of the car you passed in your side mirror
• You can see the headlights of the car you passed in your rearview mirror
  Explanation:

  "You can see the headlights of the car you passed in your rearview mirror"
• Your rear bumper has passed the front bumper of the car you passed
• You can't see the car you passed by looking to your right