C would be 16 and b would be 8 square root of 3 so the answer would be a
The ratio A/r² would represent

which is the circumference of a circle divided by its diameter.
You can see this because the area of a circle is

r² and if you divided that by the radius squared, you are given pi which is the circumference of a circle divided by its diameter.
Since it says ''times'', you have to change the mixed numbers into fractions which will turn the equation into 10/3 x 13/5 which = 130/15. When you turn that into a mixed number, it changes into 8 10/15 or 8 2/3.
ANSWER: 8 2/3