Differentiate fixed costs and variable costs. 1  Total cost is the sum of fixed and variable costs.  Variable costs change according to the quantity of a good or service being produced. The amount of materials and labor that is needed for to make a good increases in direct proportion to the number of goods produced.
Xtrata is a top five producer of copper, thermal coal, coking coal, ferrochrome, zinc and nickel and has operations in 19 countries. The company's copper production in 2010 was over 900 thousand metric tons and it has copper facilities located in Australia, Chile, Peru, Argentina, and Canada.
Coming in at the No.10 spot is the Laramide Porphyry copper cluster of Arizona, New Mexico and Sonora (Mexico). The Morenci open pit, located in southwest Arizona, is the largest copper-producing operation in North America, and majority owner Phelps Dodge Corp. has been mining this rich deposit since the 1880s.