Why did Africans sell other Africans into slavery
A. They were usually selling their enemies into slavery
B. They would receive advanced weapons like guns
C. There were no powerful empires able to organize a resistance to slave traders
D. Both a and b

They were usually selling there enemy's and in return they would receive guns an advanced weapons.

your answer would be (a)

the correct answer is:   "   3.6 % " .

          →   the unemployment rate is:   " 3.6 % " .

explanation:

to calculate the "unemployment rate" :

the "unemployment rate"   =

  [# of people unemployed] /   [working age population]   * 100 %   ;

                =   [9 million] / [250 million]     *   100 % ;

    →     note:   the units of "million" cancel out;

                    since:   " {million} / {million} = 1 " ;

                =   (9 / 250)   * 100 %   ;

                = 0.036 * 100 % ;

                =   3.6 %

answer:   the unemployment rate is:   " 3.6 % " .