Blue is on a collision course with Red and must keep clear in accordance with
rule 10 (boats on opposite
tacks). Just before the starting signal, Red changes course towards the starting
line, at which point Blue is still able to keep clear by tacking, but Blue does
not do so. Therefore Blue infringes rule
10 and will be penalized. Red does not infringe rules
16.1: Red is OK under 16.1 since her course change left Blue room
to keep clear by tacking.