Why did African merchants and rulers participated in the slave trade

Why did African merchants and rulers participated in the slave trade?

Because Instead, European traders generally relied on a network of African rulers and traders to capture and bring enslaved Africans from various coastal and interior regions to slave castles on the West and Central African coast. Many of these traders acquired captives as a result of military and political conflict, but some also pursued slave trading for profit.

the completion of the erie canal spurred the first great westward movement of american settlers, gave access to the rich land and resources west of the appalachians and made new york the preeminent commercial city in the united states.

the right answer is d