Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Date | Tournament | Winning score | Margin of victory | Runner(s)-up |
| --- | --- | --- | --- | --- |
| Feb 14, 2010 | The ACE Group Classic | −17 (68-67-64=199) | 1 stroke | Tommy Armour III |
| Mar 7, 2010 | Toshiba Classic | −18 (66-64-65=195) | 4 strokes | Ronnie Black |
| Mar 28, 2010 | Cap Cana Championship | −21 (67-66-62=195) | 2 strokes | Corey Pavin |
| Oct 24, 2010 | Administaff Small Business Classic | −17 (71-65-63=199) | 7 strokes | Mark Wiebe |
| Aug 20, 2011 | Constellation Energy Senior Players Championship | −11 (68-66-68-71=273) | Playoff | John Cook |
| Oct 16, 2011 | AT&T Championship | −23 (65-62-66=193) | 7 strokes | Mark Calcavecchia |
| Mar 25, 2012 | Mississippi Gulf Resort Classic | −14 (63-70-69=202) | 1 stroke | Michael Allen |
| Jul 29, 2012 | The Senior Open Championship | −9 (72-68-64-67=271) | 2 strokes | Gary Hallberg |
| Nov 3, 2013 | Charles Schwab Cup Championship | −17 (65-65-68-69=267) | 6 strokes | Bernhard Langer , Mark O'Meara , Peter Senior |
Question:
What was the margin of victory when the winning score was −9 (72-68-64-67=271)?
Answer:
2 strokes