Extra Exercise 1
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(a) 
Only one (yellow) arrow is shown because the mean and median coincide.

(b)
When moving the rightmost point, the median is unaffected whereas the
mean increases when the point is increasing in value. The median is
unaffected because it is the middle observation of the three. The mean
is affected by all 3 observations and be considerably affected by a
single observation (and is therefore not resistant).

When moving the rightmost point to the left, the mean gets close to and
even smaller than the median. When moving the point across the
second largest point, the median jumps from that point to the one now
being second-largest. This is because with 3 points, the median equals 
the middle (or second largest) point.

(c) 
With 5 (or another odd number) of distinct points, the median won't
change when an extra point is added with its value being equal to the
previous median value. This can be understood from the formula for the
median for an even number of points, because the median equals the
average of the two most central points (and in this case they are
equal).

Now adding an extra point does not change the median at all, no matter
the value of this extra point. This is because regardless of where the 
new point is positioned, the new middle point will be one of the duplicate 
points at the previous median value.