A metallurgist added eight substances in various combinations to seven samples of molten aluminum for the purpose of producing aluminum alloys. The metallurgist was interested in producing an alloy that had a special resistance to corrosion. The samples were distinguished by the following characteristics. Samples 1, 2, and 3 contained both tin and copper, but only samples 1 and 2 were resistant. Samples 6 and 7 contained both silver and iron, but only sample 7 was resistant. Samples 4 and 5 contained sodium, but only sample 5 was resistant. In addition, samples 1 and 7 contained zinc, silicon, and nickel. Sample 2 contained sodium, iron, and silicon, and sample 5 contained silicon and copper. Finally, sample 3 contained nickel, and sample 4 contained zinc. Assuming no interaction occurs among these eight additives, what conclusion can the metallurgist draw about these additives? Construct a table that supports this conclusion. Which one of Mill's methods did the metallurgist use? What sense of causality is involved in the conclusion?