Answer:

Explanation:
To find the potential difference between
and
, we just need to observe which vertical coordinates belong to these given values.
From the graph, we observe that
correspond to
, because they form the point
which is given in the graph.
With the same reasoning, we observe that
corresponds to
, because they both together form the points
.
Now, the potential difference between the given distances, we just need to subtract

Which also refers to the variation of the potential.
Therefore, the potential differential is 