please show as much logic and steps as possible, thank you
8. Find the volume of the solid obtained by rotating the region bounded by ONE of the TWO given sets of curves.
a) y = 2x + 4, y = 0,x = 0, x = 4, spin about the x = 6. b) y = 2 - x, y = 0, x = 0, spin about the y = 4.