Utilize the input text as a context reference, choose the right relationship between 'Apple Inc' and 'iPhone' from the options.
Options: headquarters location, founded by, location of formation, product/material produced

The housing index (.HGX) rose 1.64 percent on the data, outperforming the overall stock market, which fell after Apple Inc (AAPL.O) late on Tuesday gave a fourth-quarter revenue forecast that fell short of estimates and missed some targets for iPhone sales.
product/material produced