oleh Berhane, Tesfahun; Bahir Dar University , Adam, Molalign; Bahir Dar University , Awgichew, Guriju; Bahir Dar University , Haile, Eshetu; Bahir Dar University

oleh Berhane, Tesfahun; Bahir Dar University , Shibabaw, Nurilign; Bahir Dar University , Awgichew, Gurju; Department of Mathematics Bahir Dar University , Kebede, Tesfaye; Department of Mathematics Bahir Dar University