1. Department of General Education, Anhui Xinhua University, Hefei 230088, China
2. Department of Mathematics, The Islamia University of Bahawalpur, Bahawalpur 63100, Pakistan
3. Department of Basic Sciences, Balochistan University of Engineering and Technology Khuzdar, Khuzdar 89100, Pakistan
4. School of Mathematics and Physics, Anhui Jianzhu University, Hefei, Anhui 230601, China