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:
| Year | Tournament | Winner | Margin of victory | Winners share ( $ ) | Par | Course length |
| --- | --- | --- | --- | --- | --- | --- |
| 1949.0 | U.S. Open | Cary Middlecoff | 1 stroke | 2000.0 | 71.0 | yd (m) |
| 1975.0 | U.S. Open | Lou Graham | 2 strokes (90) | 40000.0 | 71.0 | yd (m) |
| 1988.0 | U.S. Senior Open | Gary Player | 2 strokes (90) | 65000.0 | 72.0 | yd (m) |
| 1990.0 | U.S. Open | Hale Irwin | 91 Holes | 220000.0 | 72.0 | yd (m) |
| 1999.0 | PGA Championship | Tiger Woods | 1 stroke | 630000.0 | 72.0 | yd (m) |
| 2006.0 | PGA Championship | Tiger Woods | 5 strokes | 1224000.0 | 72.0 | yd (m) |
Question:
When hale irwin is the winner what is the margin of victory?
Answer:
91 Holes