In this question, can I choose radius of B as 0.1? So Radius of A= 12.1

In this case Difference of Circumfrence = 22.1 * 3.14 = 69

If radius of B = 1, Radius of A = 13

In this case Difference of Circumfrence = 24 * 3.14 = 75

So i Picked D. Though Answer is A.

I think I am doing something wrong in the first case. Need help to understand where i am going wrong here.