Question
A and X are approaching a leeward mark to be left to starboard. When X reaches the two-length zone she is clear ahead of A. X bears away and at position 2 A gains a leeward overlap. X maintains her course until position 3 when A protests. What should the call be?

Answer
When X reaches the two length zone, X and A become subject to rule 18.2(c). A is keep clear boat until both boats have passed the mark.
Under rule D1.1(a), when X bears away and the boats become overlapped, X becomes subject to rule 17.2 and must not sail below her proper course. At position 2 she is sailing a proper course to pass the mark.
At position 3 X’s course is no longer a proper course to pass the mark and therefore she breaks rule 17.2. Penalize X.