On the one hand, it is not clear that the boats are "about to round or pass" the mark, for two reasons:
On the other hand,
Even if RRS 18 applies, it is not easy to say which boat enjoys the room granted to it by 18.2(a). The boats are certainly overlapped, but 18.2(a) only gives rights to room to the 'inside' boat, and it isn't clear which of these two boats is 'inside'. ISAF case 2 helps us a little, because it says that "When rules 18.2(a), 18.2(b) and 18.2(c) do not apply, right of way is determined by the relevant rule in Section A of Part 2". At entry into the zone, both Green and Yellow are about equidistant from the mark, though when we get a little further into the sequence, Yellow comes closer to the mark than Green.
Let us imagine that Green starts to luff in an attempt to get Yellow to tack
Before clicking on a letter to see what we think, decide for yourself if you think the statements are true or false...
Assuming RRS 18 does NOT apply:
Assuming RRS 18 DOES apply, and that Yellow is the inside boat:
Let's have a look at the next page to see what might happen if Yellow sails Green off the mark.
©2018 Lester Gilbert