OK, here’s my analysis of the scenario in the posting ‘Baker 2012’ on this blogsite. First, as everybody agrees, A entered the zone clear ahead of both her teammate B and her opponent X, and as she never left the zone or tacked, A is therefore entitled to mark-room from both boats. Except possibly for a brief moment when she is jibing, A also has right of way over X. She doesn’t break rules 15 or 16 after position 5 in this scenario, but if she had, she would have been exonerated under rule 18.5 because from that point on, she was sailing to the mark and then sailing her proper course at the mark.
As windward boat, X was required to keep clear of A and she clearly didn’t do so. So X needs to take a penalty (one turn, if she does so voluntarily; two, if the umpires get involved).
Now that we’re all agreed that X re-entered the zone clear ahead of B (see my post, ‘Graphic animations’), we should all agree that B is required to give X mark-room. At position 6, X is on port tack and B is on starboard, so X is required to keep clear of B, which she clearly isn’t doing. However, she’s exonerated under rule 18.5 because she’s sailing to the mark. By the time X is at the mark, B is a windward boat required to keep clear, so it’s irrelevant whether X is on her proper course (though it would be interesting to hear your opinion – in position 7, is X on her proper course?).
So we’ve got B failing to keep clear of X and X failing to keep clear of A. Both boats should do their turns, or, if they're protested and don't spin, the umpires should tell them to take two turns. Note that there’s no additional penalty for hitting the mark, as they’ve broken rules of Part 2 as well – see rule 44.1(a).
As it happened, both X and B took voluntary single-turn penalties. But this raises another question – did either team gain an advantage? In order to decide that issue, we must determine what combination the teams had just before the fouls, and compare it with the positions they had afterwards (taking into account the penalty turns).
What positions should we declare the three boats to be in, just before everything went crazy? Was A’s mark-trap about to work, so Yellow had a 1-2? Or did X break the trap by jibing behind A, so Yellow had at best a 1-3? We’ll look at those questions, and tell the rest of the story, in a later post.