Commonwealth Bank of Australia (CBA), the nation\'s largest retail bank, on Wednesday posted an unaudited first-quarter profit of 1.8 billion AU dollars (1.88 billion U.S. dollars). In its September quarter trading update, the bank said its unaudited cash earnings for the three months to September were approximately 1.85 billion AU dollars, up six percent from 1.75 billion AU dollars in the same period of the previous year. The bank said its revenue growth continued to reflect a combination of conservative business settings, relatively slower credit growth and elevated funding costs. CBA said that it had managed to control costs to maintain its profitability. But it has seen a fall in the quality of its business loan portfolio due to tough economic conditions. \"A slight deterioration in corporate credit quality in the quarter reflected the continuing difficult operating environment in certain sectors of the economy,\" CBA said in the update.