1. Institute of Mathematics and Digital Technology, Mongolian Academy of Sciences, Ulaanbaatar 13330, Mongolia
2. Department of Applied Mathematics, National University of Mongolia, Ulaanbaatar 14201, Mongolia
3. Department of Mathematics, Sungkyunkwan University, Suwon 16419, Republic of Korea
4. School of Applied Sciences, Mongolian University of Science and Technology, Ulaanbaatar 14191, Mongolia