Under dual wage systems, employers were encouraged to hire blacks instead of whites for which of the following reason(s)? Group of answer choices a. Blacks got lower wages, so they cost their employers less. b. The lower wages of blacks tended to keep down the wages of the white workers because if whites demanded higher wages, they could be replaced with lower-paid black workers. c. Racial tensions could be used to play black and white workers against each other. d. All of the above are valid reasons which encouraged employers to hire blacks instead of white workers