Sagot :
A. 40ml
I don't have the exact formula so I tried solving it logically.
If you divide it in half, it will be 30ml for 6%. Following that should be 35 ml for 7%, 40ml for 8%, 45 ml for 9%, 50 ml for 10%, 55 ml for 11% and 60 ml for 12%.
Hope it helps!