Metal corrosion

This task is about fair testing and reading information from a graph.
10 gram of each of the following metals: copper, iron, magnesium, and zinc were polished, and then left to corrode on a shelf in a laboratory for 3 months. They were then polished again, the mass loss worked out, and the results graphed.
 
Mass loss of metals
metal corrosion graph

Question

 a)  Which metal corroded the most?

    • Copper

    • Iron

    • Magnesium

    • Zinc

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b)  How much iron corroded?  g.

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c)  How much zinc was left?  g.

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d)  What was the total mass of all the metals after 3 months? (Show your working).
 g.

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e)  Write an aim for this experiment.

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f)  Why were the metals polished at the end of 3 months?

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g)  Why was the starting mass of each metal the same?