First Author:   Michael Zarichnyi University of Rzeszow, Lviv National University mzar@litech.lviv.ua   Department of Mathematics, Lviv National University, 1 Universytetska Str. Lviv, 79000, Ukraine       Second Author: Oleksandra Hubal Lviv National University topology@franko.lviv.ua   Department of Mathematics, Lviv National University, 1 Universytetska Str. Lviv, 79000, Ukraine   +380322964218(Phone)