Circle

Paragraph for next 2 questions
Let M={(x,y)∈ℝ×ℝ:x2+y2≤r2} where r>0.
Consider the geometric progression an=‌

1

2n−1

,n=1,2,3,....
Let S0=0 and, for n≥1, let Sn denote the sum of the first n terms of this progression. For n≥1, let Cn denote the circle with center (Sn−1,0) and radius an, and Dn denote the circle with center (Sn −1,Sn−1 ) and radius an.