Slow times.....no profits!
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It takes 5 units of Iron to make a gun. Iron is running 0.37 a unit.
I pay 0.50 per unit of production. It takes 5 units of production to produce a gun.
So
0.37 times 5 is 1.85
0.50 times 5 is 2.50
That is 4.35 cost