It's probably 15-25. Results from 25 uses:
20, 16, 23, 20, 18, 20, 19, 23, 15, 22, 15, 24, 18, 15, 20, 21, 19, 18, 18, 23, 21, 18, 20, 23, 17
Cristiona 02:09, 21 January 2008 (MST)
Just used about 20 more. Ranging from 15-25. Those are round numbers, so I'm calling that accurate. Cristiona
