Tinjauan yuridis mengenai pengaturan divestasi dalam penerapan undang-undang nomor 4 tahun 2009 tentang pertambangan mineral dan batubara : studi kasus kegiatan pertambangan mangan di Provinsi Nusa Tenggara Timur = The legal analysis of divestment arrangements within the application of act no 4 of 2009 on mineral and coal mining mineral and coal act with a case study on manganese mining activities in East Nusa Tenggara Province