we know that
The average rate of change is equivalent to the slope of the graph between the two points.
[the average rate of change]=[change in y / change in x]
for x=0 y=4
for x=4 y=4
then
change in y=4-4-----> 0
change in x=4-0-----> 4
[the average rate of change]=[0 / 4]------> 0
the answer is
0