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You have to expend money and/or energy in aquiring materials and labour to build the water mill. Money and/or energy in maintaining it.
by el_oni 5y ago
You have to expend money and/or energy in aquiring materials and labour to build the water mill. Money and/or energy in maintaining it.
- Aerroon 5y agoSure, but that's kind of missing the point. We're taking advantage of rain and rivers with the water mill. The water flows downhill and we benefit from it, yet we don't have to do any work to get that water back uphill. We gain more energy out of it than we put in.