Sales of the previous-generation iPhones were 17.1 million units in Apple's fiscal Q3, below the expectations of many analysts. But new CEO Tim Cook predicts strong results from the new iPhone 4S for this new quarter. The four-year-old smartphone is now Apple’s single biggest producer of revenue. Elsewhere, Apple sold 11.1 million iPads last quarter and 4.9 million Mac computers. The once high-flying iPod saw sales drop 27% to 6.6 million units, though it remains profitable. Total Apple revenue for the quarter grew 39% to $28.27 billion, with gross margins improving from 36.9% to 40.3%. Looking forward, Apple said it sold four million of the new iPhone 4S models in just three days.