1. Faculty of Exact and Natural Sciences, School of Physical Sciences and Mathematics, Pontifical Catholic University of Ecuador, Av. 12 de Octubre 1076 y Roca, Apartado, Quito 17-01-2184, Ecuador
2. Department of Mathematics, University of Sargodha, Sargodha 40100, Pakistan
3. Department of Mathematics and Statistics, College of Science, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia
4. Department of Mathematics and Computer Science, University of North Carolina at Pembroke, Pembroke, NC 28372, USA