I^*=I_* \Longrightarrow \left .\begin{array}{l}\forall (\varepsilon>0) (\delta_1 \in \Delta)~ t.d. ~S(\delta)-I^* \leq \frac{\varepsilon}{2} \\ \forall (\varepsilon>0) (\delta_2 \in \Delta)~ t.d. ~I_*-s(\delta) \leq \frac{\varepsilon}{2} \end{array} \right \}+ \Longrightarrow