Answer :
From my research, the image below belongs to the question. From what is seen in the image, there are 2 arcs already drawn with respect to the new vertex. The third arc corresponds to the point where the line DM is made. This line is similar to line BC. So at the point where the second and third arcs would meet, it would be a point similar to a point on line AB.

The correct answer to this question is "The third arc should cross the third arc." Line DM is another line in which the third arc is present - which is also very similar to line BC. It will be the same as the point on line AB, where the third and second arc meet.