Use trigonometry to find the angle between the segments 3 and 6.
∠XOB = arccos(3/6) = 60°
The measure of arc AB is double that angle, since the figure is symmetrical about the line containing the segment of length 3.
m(arc AB) = 2·60° = 120°
I believe it is 8,000 grams :).
The letter C stands for the Circumference of the circle
