- Vettel has to be on the Singapore podium to become champion.
- if Alonso is on the podium, Vettel can’t do it.
- if Hamilton wins, Vettel can’t do it.
Vettel is now virtually champion
In detail:
To become champion, Vettel requires one of the following three scenarios:
1. Vettel wins; Alonso 4th or lower; Button/Webber 3rd or lower.
2. Vettel 2nd; Hamilton 3rd or lower; Alonso 8th or lower; Button/Webber 5th or lower.
3. Vettel 3rd; Hamilton 4th or lower; Alonso 9th or lower; Button/Webber 7th or lower.
In reality:
If Vettel isn't out for the rest of the season, he's champion.
Now:
1 - Vettel
2 - Button
3 - Webber
4 - Alonso
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1 - Vettel
2 - Button
3 - Alonso