How ghana, mali, and songhai flourish?

The Ghana, Mali, and Songhai flourished by Gold-Salt Trade .

Explanation:

Three of the largest western African buying and selling states were Ghana, Mali and Songhai. It starts from Ghana at just 300 C.e  

The exchange in gold, oil, and products between Northern Africa and Sub-Saharan Africa continued, and the invasion of Morocco by the Songhai began in the 16th century BC.

The prosperous and very well-organized countries in Ghana, Mali, and Songhai have resolved tribal discord and merged traditional views with Islam's secular ambitions.

Gold was precious and at the period there had been no salt and the only means of preserving food. The West African Empires had several mining facilities both for and exchanged with others (mostly Europe) nations, enabling their economies to flourish.

during world war ii