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 | Team | Name | Position | Years in NBA | Notes |
| --- | --- | --- | --- | --- | --- |
| April 23, 2009 | Houston Rockets | Dikembe Mutombo | C | 18 | Suffered a season-ending injury |
| May 21, 2009 | Free agent | Sam Cassell | G | 15 | Became an assistant coach of the Wizards |
| September 3, 2009 | Free agent | Bruce Bowen | F | 12 |  |
| October 22, 2009 | Free agent | Mark Madsen | F | 9 | Became an assistant coach of the Utah Flash (D-League) |
| October 23, 2009 | Free agent | Bobby Jackson | G | 12 |  |
| October 23, 2009 | Free agent | Tyronn Lue | G | 11 | Became the director of basketball development of the Celtics |
| November 5, 2009 | Free agent | Darrick Martin | G | 14 | Named assistant director of player development of Timberwolves |
Question:
how many players retired after playing 12 years?
Answer:
2