Volume of half-cut cylinder

Question

I'm having trouble obtaining the answer for this practice-test problem.

I'm taking the volume of the whole cylinder as if it weren't cut then subtract the portion cut off. But I'm not getting any of the answers below. Any hints will be greatly appreciated. Thank you all.

Answer 1

$d=18$ (because angle=45 degree) then $r=9$

$V=(1/2) 18 r^2 \pi + 6 r^2 \pi=1215 \pi $

Answer 2

Suppose you have a cylinder 30cm long. Then you can slice it in half on the slant, to get two identical pieces like the one in your diagram. So what is the volume of each piece?