Answer A: 84π
Answer B: I'm also confused. If anyone else knows can you please help me also. Sorry for not answering B. I hope this helps though. 
Explanation:
Answer A: 
V=1/3π 6^2 (7) Since 12 is a diameter you half it which is 6
V=1/3π 36(7)
V=1/3π 252
V= 252π/3
V=84π