The Mongol Yuan dynasty, through the Bureau of Buddhist and Tibetan Affairs, or Xuanzheng Yuan, ruled Tibet through a top-level administrative department. One of the department's purposes was to select a dpon-chen ('great administrator'), usually appointed by the lama and confirmed by the Mongol emperor in Beijing. The Sakya lama retained a degree of autonomy, acting as the political authority of the region, while the dpon-chen held administrative and military power. Mongol rule of Tibet remained separate from the main provinces of China, but the region existed under the administration of the Yuan dynasty. If the Sakya lama ever came into conflict with the dpon-chen, the dpon-chen had the authority to send Chinese troops into the region.

Answer this question, if possible (if impossible, reply "unanswerable"): What was a dpon-chen?
great administrator