Hubungan timbal balik struktur modal dan posisi persaingan berdasarkan tipe strategi cournot dan bertrand pada perusahaan manufaktur sub sektor food and drugs retailers di Bursa Efek Indonesia periode penelitian 2007-2014 = The reciprocal relationship between capital structure and competitive position based on cournot and bertrand stretegy of manufacturing on food and drug retailers companies in Indonesia stock exchange from the 2007 2014 period