[1] Univ Nusa Cendana, Fac Sci & Engn, Dept Math, Kupang 85001, Nusa Tenggara T, Indonesia
[2] Prov Govt Moluccas, Dept Educ & Culture, Ambon 97125, North Maluku, Indonesia
[3] Univ Padjadjaran, Dept Math, Postdoctoral Program, Jln Raya Bandung Sumedang Km 21 Jatinangor, Kab Sumedang 45363, Jawa Barat, Indonesia
[4] Univ Padjadjaran, Dept Math, Jln Raya Bandung Sumedang Km 21 Jatinangor, Kab Sumedang 45363, Jawa Barat, Indonesia
[5] Univ Nusa Cendana, Fac Sci & Engn, Dept Comp Sci, Kupang 85001, Nusa Tenggara T, Indonesia