Red has fouled Blue. As she tacks, Red is subject to rule 13. After that, Red is subject to rule 11 and must keep clear, which she does not do. Blue establishes an inside overlap from clear astern after Red passes head to wind inside the zone and is subject to rule 17. Because Blue is now inside overlaped Red shall give her mark-room (see rule 18.2(a)). Blue may sail her proper course but not above it. The collision occurs because Red keaps not clear and does not give mark-room. Therefore Red breaks rule 18.2(a) and rule 11. Rule 18.3 does not apply because the mark has to be left on starboard.