The main items traded were gold and salt. The gold mines of West Africa provided great wealth to West African Empires such as Ghana and Mali. Other items that were commonly traded included ivory, kola nuts, cloth, slaves, metal goods, and beads.
Answer:
Examples of a secondary source are: Publications such as textbooks, magazine articles, book reviews, commentaries, encyclopedias, almanacs.
Before the panama canal people from East coast of America who wanted to go to Asia had to either sail around south America which took months or sail towards Asia and go around Africa which took even longer. The panama canal was a short cut right in the middle of central America which cut navigation time in half. Hope I helped. :)
The answer would be thomas jefferson