1. Department of Technical Mechanics, Yanka Kupala State University of Grodno, Ozheshko Street 22, Grodno 230023, Belarus
2. Department of Mathematical Analysis, Differential Equations and Algebra, Yanka Kupala State University of Grodno, Ozheshko Street 22, Grodno 230023, Belarus
3. Department of Mathematical and Information Support of Economic Systems, Yanka Kupala State University of Grodno, Ozheshko Street 22, Grodno 230023, Belarus