The set of optimal solution for the problem that we have introduced can be computed by considering the theory of multi- criteria optimisation. We will talk about Pareto-optimal solutions, non-dominated solutions, EP optimal solutions. The mathematical definition is given. The solution xi is non dominated (Pareto-optimal, EP optimal) if it does not exist a solution xj such as the written inequality holds. To make it simple considering a Pareto-optimal solution if we try to improve one objective function at least another one is worsened.

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