How Many time you knock your door per day?

Have you ever think of this question, it would be a very large times.

Each time you open the door or close the door.And how many people knock with the same door?

Such as the paper cash, it would be very dirty if too many people touch them. So the times is not so important here, you should clean your pvc door and wood door knobs or handles each week. Expecial the office working place.