Set A of 8 positive integers may have the same element and have 39. And set B of 8 positive integers must have different elements and have 39. When m and n are the greatest possible differences between 39 and other elements’ sums in set A and set B, respectively, m-n=? Select the correct option.
A) 20  B) 23  C) 21  D) 25  E) 26
This is maximum-minimum. Hence, 39-(1+1+1+1+1+1+1)=32 and   39-(1+2+3+4+5+6+7)= 
<gadget id="calculator">  39-(1+2+3+4+5+6+7)</gadget>
<output>11</output>
11. So, 32-11=21. The correct answer is 21.
<result>C</result>
Set A of 8 positive integers may have the same element and have 39. And set B of 8 positive integers must have different elements and have 39. When m and n are the greatest possible differences between 39 and other elements’ sums in set A and set B, respectively, m-n=?