1. Department of Applied Mathematics, University Politehnica of Bucharest, 060042 Bucharest, Romania
2. Academy of Romanian Scientists, 050094 Bucharest, Romania
3. Fundamental Sciences Applied in Engineering-Research Center (SFAI), University Politehnica of Bucharest, 060042 Bucharest, Romania
4. Faculty of Mathematics and Computer Science, University of Lodz, Banacha 22, 90-238 Lodz, Poland
5. Financial Mathematics and Actuarial Science (FMAS)-Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia