Mostafa Tahmasebi CREG, Université de Grenoble (UPMF)   CREG, Université de Grenoble (UPMF), BP 47 Grenoble, cedex 9, Isere 38040 France   Mostafa.Tahmasebi@doctorant.univ-grenoble.fr             JEL Areas: C : Mathematical and Quantitative Methods C6 : Mathematical Methods and Programming: General