Guret and Associate (2002),Section 12.1. A military telecommunication system connecting 9 sites is given in Figure 6.43.

Guéret and Associate (2002),Section 12.1. A military telecommunication system connecting 9 sites is given in Figure 6.43. Sites 4 and 7 must continue to communicate even if as many as three other sites are destroyed by enemy actions. Does the present communication network meet this requirement? Use AMPL and Solver to work out the problem.