Apple is due to report its earnings for the past three months Tuesday as the company faces challenges in its key smartphone and tablet markets — from competitors and from itself.

Analysts expect that Apple will have strong iPad sales as the company reports its earnings for the past three months, as the bulk of the sales of the new iPad flow in.

The wild card in this quarter’s report is the iPhone. In its last earnings call, the company reported that it had sold 35.1 million iPhones. But iPhone sales are expected to be a bit slower as potential buyers wait to see what the company may unveil this fall.

The company has run into that problem in the past. When it missed estimates in October 2011, Chief Executive Tim Cook cited anticipation for the next iPhone — and the rumors flying about the device — as a reason that iPhone 4 sales had dropped. The iPhone 4S, of course, then went on to be Apple’s best-selling iPhone ever.

Accounting for a similar pattern ahead of the next iPhone’s (as-yet-unconfirmed but completely expected) launch in the fall, analysts have been revising their estimates downward to hover around the 29 or 30 million mark.

AT&T and Verizon reported solid iPhone sales this quarter, with Verizon saying it sold 2.7 million units in the last quarter and AT&T saying Tuesday morning that it has sold 3.7 million.

How much money do analysts think Apple made this quarter? According to a collection of analyst estimates compiled by Fortune’s Philip Elmer-DeWitt, analysts say that they expect sales of about $37 billion in sales from Apple this quarter. Tech bloggers, whom Elmer-Dewitt has found have always been more bullish than their professional counterparts, are predicting that Apple will have $41.5 billion in sales.

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