Question
In a steady wind boat A, on port tack, reaches the two-length zone of a starboard-hand windward mark clear ahead and slightly above the layline. The next leg is a close reach. A stops with her bow 1½ lengths to windward of, and level with, the mark. Boat X, on the port tack layline, tries to sail between A and the mark, but A bears away onto a beam reach to 'close the door', and X makes contact with A and the mark. X protests. What should the call be?

Answer
Because A is clear ahead of X when she enters the two-length zone, she has right of way and X must keep clear of A until both boats have passed the mark. In addition, A is not constrained by rule 16, Changing Course, when she changes course to round the mark.
However A may not sail below her proper course when X is overlapped to leeward because she is no longer on a windward leg. At position 3 A is clearly below her proper course and X is passing her to leeward. A breaks rule 17.2.
Penalize A.
X breaks rule 18.2(c) by failing to keep clear. However, X would have kept clear if A had not broken rule 17.2, and she is therefore exonerated for breaking rules 18.2(c) and 31.1 under rule 64.1(b).