Napata, the capital of the Nubian Kingdom, became a center of trade?

Ancient Nubian cultures were sophisticated and cosmopolitan, as the region served as a major trading center for goods from the African interior, Arabian desert, and Mediterranean basin. From sub-Saharan Africa, Nubian communities traded gold, ivory, ebony, and animal pelts.

It was an ideal center for trade because it was along the Nile River and near overland trade routes.

answer; the automatic system because it is a "gut reactor"