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 | To par | Margin of victory | Runner-up |
| --- | --- | --- | --- | --- | --- |
| Apr 22, 2007 | Zurich Classic of New Orleans | 69-67-68-69=273 | −15 | 3 strokes | Ken Duke |
| Feb 8, 2009 | Buick Invitational | 69-69-71-68=277 | −11 | 1 stroke | John Rollins |
| Mar 13, 2011 | WGC-Cadillac Championship | 67-70-68-67=272 | −16 | 2 strokes | Dustin Johnson |
| Jul 3, 2011 | AT&T National | 70-69-62-66=267 | −13 | 2 strokes | K. J. Choi |
| Aug 26, 2012 | The Barclays | 65-69-71-69=274 | −10 | 3 strokes | Brandt Snedeker |
Question:
What was the to par of the tournament that had Ken Duke as a runner-up?
Answer:
−15