I believe it would be 1/10 @B's 30. The foul on A occurred after the completion of penalty administration (announcing the foul), therefore the order of occurance applies. B's foul creates a new series when ball marked at B's 15, ump 
would then do a U-turn and bnring ball back to B's30 for A's naughty talk. Using NFHS signals, this would be the protocol :
(1) signals 7 & 38, ump brings ball to B's 15;
(2) signal 8, ref signals 1st down;
(3) signals 7 & 27,ref returns ball to B's 30.
Concur (mostly). But the potentially confusing circumstance is the fact that these are not the usual bang-bang fouls that occur in the same general time frame (like mutual shoving, or a late hit with a retaliation block). In this case, A88's UNS foul occurred clearly after the penalty for B99's UNS foul had been
completed. OK, so that removes the provision to 'cancel' the penalties for both UNS fouls, and play 3rd down at the dead-ball spot. So, we'd have to penalize B99's foul to the B-15. Then we'd have to penalize A88's foul back to the B-30. But, is it 1st/10? Or is it 1/25?
Don't get confused by the "...and none of the penalties have been completed,..." in 10-1-5. Since B99's penalty had been completed, yes, they are penalized in the order of their occurrence, per 10-1-5. Then we have to follow 5-2-7, as A88's foul occurred between series, due to the completion of B99's penalty. After the distance penalties are enforced, then, because B99's penalty includes a first down, the line-to-gain is established after A88's penalty is enforced. 1/10. So, the net effect is to give Team A a new series at the dead-ball spot.
Personally, I don't like this part of the rules. If we are already in the process of announcing one foul, these guys need to have enough self-control to avoid doing anything stupid. If that is Team B, they suffer sufficiently in giving up another 15 yards plus a first down. But, if Team A does something stupid, yeah, they give back the distance, but they still get 1/10. I think it would be more effective if this resulted in 1/25. But, I'm not in charge.
I believe the NCAA wants both of these fouls to be treated as UNS fouls, so each player gets one credited to their UNS counters. Should it be their second UNS, they get to go to the dressing room.
As for the announcements, I would expect the R to fully complete the announcement for B99's foul (with appropriate hand signals):
"After the ball became dead, unsportsmanlike conduct, number 99, defense - shoving the face of the ball carrier. That's a 15-yard penalty, and a first down. This is number 99's first unsportsmanlike conduct foul of the game."
Then, the second foul would be reported, and completed, with the announcement (with appropriate hand signals): "After the penalty for number 99's foul was accepted, unsportsmanlike conduct, number 88, offense - abusive language toward an opponent. That's a 15 yard penalty. By rule, since both fouls occurred before the ball was declared ready for the next down, the line-to-gain is set after both distance penalties are enforced. 1st and 10, at the Notre Dame 30 yard line.
This is number 99's first unsportsmanlike conduct foul of the game."
Yeah. A lot to say. But Pereira would say something like, "A very good explanation by the Referee!"
