| Benicio Del Espada |
If you had 10 levels of each, it would be 15. There are no official PF rules for epic (over 20) levels, but it used to be sorcerer BAB for all classes after 20. You didn't get more than 4 attacks total in your BAB, however. That capped at BAB +20.
So, with 20 levels of each, you would have a BAB of +30, and 4 attacks at 30/25/20/15.
I'm a little confused by the question, though. Did I answer it? LOL