RE: Brain needs math help....toro,
I think it's something similar to this...
600a + 3.50b = 4,200,000,000
where a = ounces of gold and b = pounds of copper
I don't know if those prices are correct, I just worked backwards to determine them.
If we go back a year and those prices are not correct, then I am not sure how how came up with the quantities he put down.
(yes, I could look them up, but I'm watching hockey tonight, so it's a lazy evening.) :)