O.A. Teteneva1, R.A. Kochkarov2, P.E. Ryabov3, A.M. Kochkarov4

1–3 Financial University under the Government of the Russian Federation (Moscow, Russia)
4 North Caucasian State Academy (Cherkessk, Russia)
1 oateteneva@yandex.ru, 2 rkochkarov@fa.ru, 3 peryabov@fa.ru, 4 kaf_math@ncsa.ru