An alloy of zinc, magnesium and copper contains 80% copper, 15% zinc and 5% magnesium. Another alloy of copper and magnesium is melted with only the first and the mixture contains 75% copper, 5% zinc and 20% magnesium. What is the percentage of magnesium in the second alloy?
1
22.50%
2
27.50%
3
30%
4
25%