I've not seen this before but to solve it I would calculate the area for both and subtract the smaller from the larger.
36 x 36 = 1,296
1296 x 3.14/4 = 1,017.36
16 x 16 = 256
256 x 3.14/4 = 200.96
1017.36 - 200.96 = 816.4 yd
So I would go with B. which is already selected, so you're good to go.
Hope this helped! <3