How many pounds of powder coat to buy?

Hey guys,

I have a friend who got ahold of a powder coat gun and oven through his work. He said I have the option of using it if I pay for the powder. I am trying to spray all four of my brake calipers (4 pot front 2 pot rears) and my intake manifold.

Does anyone have any clue as to how many pounds of powder I should purchase to be able to complete this job?

Thanks everybody!