I can only answer 5, use my answer to help find 6.
Answer:
The volume is 259,824,773,000
Explanation:
r, or radius is half of the diameter. So we are left with (4 * pi (also known as 3.14159)* 3958.5^3)/3
(7.7947432 * 10 ^ 11) / 3 = 779,474,320,000 / 3
Which is equal to 259,824,773,000 as the volume.
I hope this solves 5 and helps you with 6.