How can we check a solution to the Traveling Salesman Problem

[Strange]

12 minutes ago, studiot said:

Further suppose we consider the path ABACADAEA.

That breaks the rules of the TSP - each node should only be visited once. 

4 hours ago, studiot said:

How much area does the optimal solution enclose?

And since n now = 2, your formula becomes

Having two nodes is a degenerate case as there is only one route.