1. Department of Applied Mathematics, University Politehnica of Bucharest, 060042 Bucharest, Romania
2. Academy of Romanian Scientists, 54 Splaiul Independentei, 050094 Bucharest, Romania
3. Fundamental Sciences Applied in Engineering-Research Center (SFAI), University Politehnica of Bucharest, 060042 Bucharest, Romania
4. Financial Mathematics and Actuarial Science (FMAS)-Research Group, Department of Mathematics, Faculty of Sciences, King Abdulaziz University, Jeddah 21589, Saudi Arabia