What was the name of the last great state to occupy the niger river region in africa prior to european arrival in the region?

What do sellers do if they expect the price of goods they have for sale to increase dramatically in the near future? store the goods indefinitely regardless of when the price rises store the goods until the price rises and then try to sell them sell the goods now and try to invest the money instead of resupplying sell the goods now but try to get the higher price for them