Shares in Anglo American soared 11% on the JSE and 9% in London yesterday after the global mining firm announced plans to lower costs at its iron ore mines in South Africa and Brazil and a boost in its total annual output for the steelmaking ingredient. The world's fifth-largest miner by market capitalisation said its fourth-quarter production was up 3% from the prior year, but output in key commodities was mixed.The results update pleased investors who have been on tenterhooks as Anglo battles low commodity prices and slowing growth in China - factors that have forced mining firms around the world to cut spending to preserve cash.Anglo shares have fallen 77% since the beginning of last year.The company has suffered more than its rivals as it has higher-cost iron ore operations than competitors BHP Billiton and Rio Tinto.Anglo has said it would sell assets, suspend dividends until the end of this year and whittle down to three divisions to cope with the fall in commodity prices.Anglo's Kumba Iron Ore said yesterday it would scale back operations, cut costs and retrench 4000 employees at Sishen, the largest iron ore operation in Africa."The market is positive that they are taking the steps to rightsize the company,"Avior Capital Markets equity analyst Wade Napier said.Production at Kumba fell 7% to 44.9million tons last year.The miner also said annual production of thermal coal, nickel, copper and diamonds fell last year, although platinum output rose 25% to 2.3million ounces. ..