A given alloy contains 20% copper and 5% tin. How many pounds of copper and of tin must be melted with 100 lb of the given alloy to produce another alloy analyzing 30% copper and 10% tin? All percentages are by weight.
A. 20.5 lb copper and 4.5 lb tin
B. 17.5 lb copper and 7.5 lb tin
C. 19.5 lb copper and 5.5 lb tin
D. 18.5 lb copper and 6.5 lb tin