Convert the following passage into a flowchart. The earth contains a large number of metals which are useful to man. One of the most important of these is Iron. The Iron ore which we find on the earth is not pure. It contains some impurities which we must remove by smelting. The process of smelting consists of heating the ore in a blast furnace with coke and limestone and reducing it to metal. Blasts of hot air enter the furnace from the bottom and provide the oxygen which is necessary for the reduction of the ore. The ore becomes molten, and its oxides combine with carbon from the coke. The non-metallic constituents of the ore combine with limestone to form a liquid slag. This floats on top of the molten iron and passes out of the furnace through a tap. The metal which remains is pig iron. We can melt this again in another furnace — a cupola — with more coke and limestone and tap it out into a ladle or directly into moulds. This is cast iron​