All of the above responses contribute to the wealth of the kings of Ghana. The mining of salt and selling it to neighboring regions allowed them to accumulate wealth. Additionally, the kings of Ghana controlled the trade of gold, which was highly valued and sought after. Utilizing the trans-Saharan trade route, they acquired expensive items like ivory, further adding to their wealth. Lastly, the kings of Ghana's knowledge of ironworking allowed them to produce and sell weapons to neighboring empires, which also contributed to their wealth.
