The best finding from your investigation would be:
"The demand to harvest cash crops at a cheap labor price increased the African slave trade."
This statement captures the essence of how plantations, which were focused on producing cash crops such as sugar, tobacco, and cotton, drove the demand for cheap labor, leading to an increase in the African slave trade. It emphasizes the economic motivation behind the trade, highlighting the plantations' reliance on enslaved labor to maximize profits from these lucrative crops.