How do we know so much about how many Africans were enslaved and where they went during this time?

Which best describes the“brain trust” franklin roosevelt promised to make part of his administration? a group of america’s most successful businessmen, who would fix the economya group of hoover’s economic advisers, who would undo previous damage to the economya group of smart advisers, who would assist roosevelt in guiding the nation forwarda group of military veterans, who would assist roosevelt in putting americans back to work