Also I don't check actually what is in wagon
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Okay I did small test for the given items as example:
My first solution with robots: 1:06.15
Results for high tech (without robots):
XKnight's solution: 0:17.36
My 2nd solution: 0:22.91
My 2nd solution probably will be faster with lower tech, as it is not optimised and "randomness" with smaller amount of items will be easier to get desired amount.
XKnight's solution is faster but harder to implement (I mean not placing blueprint, but setting constants for techs if not maxed tech) and keep up with tech upgrades.