[1] British University in Egypt, Misr-Ismalia Desert Rd., El Sherouk City, Serbia
[2] Department of Engineering Management and Systems Engineering, The George Washington University, 1776 G Street, N.W., Suite 110, Washington, DC 20052, United States
[3] Department of Mathematics and Computer Science, University of Maribor, PeF, Koroška cesta 160, 2000 Maribor, Slovenia
[4] Institute of Mathematics, Physics and Mechanics, Jadranska 19, 1000 Ljubljana, Serbia
[5] Faculty of Science, University of Kragujevac, P. O. Box 60, 34000 Kragujevac, Serbia Montenegro, Serbia