The CPI takes a constant basket of goods and sees how the price changes from year to year. If the price of the basket of goods increases, then there is price inflation. If the price of the basket of goods decreases, then there is deflation.
Copper and tin mainly make up bronze but other elements include phosphorus, manganese, silicon and aluminium.
Bronze is an alloy that helps make copper more useful. Copper on its own is highly malleable, resistant to corrosion and thermal, but it is also very soft. Mixing it with tin makes it much more durable and also improves its malleability and its resistance to corrosion. The levels of copper and tin in bronze vary.