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:
| Rank | Attendance | Opponent | Result | Date |
| --- | --- | --- | --- | --- |
| 1.0 | 18735.0 | Wichita State | L 68–89 | February 11, 2012 |
| 2.0 | 18613.0 | Wichita State | W 91-79 | March 2, 2013 |
| 3.0 | 18458.0 | Evansville | W 87-70 | December 29, 2012 |
| 4.0 | 18436.0 | Bradley | W 73–59 | January 28, 2012 |
| 5.0 | 18111.0 | Bradley | W 75-58 | February 2, 2013 |
| 6.0 | 18073.0 | Drake | W 91-61 | January 8, 2013 |
| 7.0 | 17954.0 | Wichita State | W 68–56 | December 28, 2008 |
| 8.0 | 17694.0 | Indiana State | W 79–66 | January 5, 2013 |
| 9.0 | 17676.0 | Northwestern | W 87–79 | December 22, 2011 |
| 10.0 | 17665.0 | Missouri State | L 65–77 | December 28, 2011 |
Question:
What's the rank when attendance was less than 18,073 and having Northwestern as an opponent?
Answer:
9.0