text: Xstrata Offers A\$7.4 Billion for WMC to Add Nickel (Update4) Xstrata Plc, the world #39;s biggest exporter of coal for power plants, offered to buy WMC Resources Ltd. for A\$7.4 billion (\$5.5 billion) in cash to add nickel and copper mines as China #39;s demand for metals grows.