Bernstein says a lower priced iPhone or a converged notebook/tablet offering could significantly boost Apple's salesApple Inc. ( AAPL) stock has rallied more than 44% over the last 12 months. Despite its strong performance, Bernstein Research senior analyst A.M. Sacconaghi believes that the stock remains relatively inexpensive. Its EV/FCF multiple is just 9x, in line with Western Digital Corp ( WDC) and Lexmark International Inc ( LXK), which are currently facing questions about secular outlook for their businesses. Apple stock worth $121 a share Assuming the tech giant’s FCF remains flat for going forward, Bernstein says the stock is still worth $121 per share, or $114 after accounting for Apple Inc. ( AAPL)’s cash pile which is largely offshore. However, most investors don’t usually sell Apple based on a specific target price or valuation. They tend to focus more on new product introductions, trajectory of revenue growth and whether future estimates appear realistic. Considering these three factors, Bernstein analyst Sacconaghi tries to figure out when is the best time to sell Apple stock. Historically, there has been a high correlation r-squared = 0.73 between the iPhone maker’s earnings multiple and the expected next-twelve month NTM revenue growth. That’s why the stock is so sensitive to speculations about new products and upgrade cycles. Apple’s FY2015 revenues expected to surpass $200 billion Apple Inc. ( AAPL) is widely expected to launch big-screen iPhone 6 later this year, along with the iWatch. Bernstein believes the iWatch is unlikely to have a strong impact on the company’s sales and profits. The research firm says a lower priced iPhone or a converged notebook/tablet offering could significantly boost the company’s sales. Sacconaghi expects Apple’s FY2015 revenues to come in at $195.6 billion with EPS of $7.10. The iPhone shipments are likely to rise 9% YoY to 185 million units. However, Bernstein’s estimate doesn’t include the iWatch. Assuming Apple sells 30 million iWatch units in FY2015 at the ASP of $250 and 30% gross margins, the company’s revenues should go up to $203 billion and EPS to $7.33. In contrast, many analysts forecast revenues of more than $215 billion and EPS of $8 or more. Bernstein says those expectations are “over-zealous.” To achieve $8 per share in earnings, the iPhone shipments must rise at more than 20% rate. Early to mid-September best time to trim positions in Apple?