It’s C.
6(1) = 6
6(2) = 12
6(3) = 18
6(4) = 24
6(5) = 30
D because if you look at all the other ones they are wrong
56.7 because it is on the hundredths place.
I would say it represents the volume function evaluated at r=5/7, or
V(5/7)=(4/3)π(5/7)² = 2.13714