Answer:
I think it is 30 inches
Step-by-step explanation:
The difference is 6 because it is what we get when we subtract 8 and 2.
Final answer: 6
The volume of a sphere of radius r is given by

For your given conditions, the volume of 1/2 a sphere becomes

Seems to match your 2nd choice:
... 1 over 24 over 322 over 7(83)