Yohana Sitorus,
Faculty of Mathematics and Natural Sains, Medan State University Jalan Willeam Iskandar, Sumatera Utara, Indonesia,
Indonesia
Sukma Dermawan Saragih,
Faculty of Mathematics and Natural Sains, Medan State University Jalan Willeam Iskandar, Sumatera Utara, Indonesia,
Indonesia
Diana Syahputri Simamora,
Faculty of Mathematics and Natural Sains, Medan State University Jalan Willeam Iskandar, Sumatera Utara, Indonesia,
Indonesia
Wahyuni Susi Sulastri Berasa,
Faculty of Mathematics and Natural Sains, Medan State University Jalan Willeam Iskandar, Sumatera Utara, Indonesia,
Indonesia