All contacts with a photo are sorted into four boxes and tested frequently.
- Box 1 **DISSATISFIED**
- Test instantly
- Correct: Move to box 2
- Wrong: Keep in box 1
- Box 2 **NEUTRAL**
- Test after three days
- Correct: Move to box 3
- Wrong: Move to box 1
- Box 3 **SATISFIED**
- Test after one week
- Correct: Move to box 4
- Wrong: Move to box 1
- Box 4 **VERY SATISFIED**
- Test after one month
- Correct: Keep in box 4
- Wrong: Move to box 1