Changing one demand weight moves the balance point exactly.
Lower C
If C's weight drops from 3 to 1, the center is recomputed.
New x
The new center x coordinate is 3/2.
xˉnew=3/2
New y
The new center y coordinate is 1.
yˉnew=1
What-if meaning
With less weight at C, the marker moves down and right to (3/2, 1).
new center=(3/2,1)