a) Functions that any reasonable person would expect the product to have, based on the advertising but also on similar products on the market. This doesn't obviate the customer's responsibility to do some research, just covers too-obvious-to-check things like if your brand new DVD recorder didn't include a DVD playback function
I returned an Iphone 3G in this spirit. "I don't know any other phone were I can't resent or forward a text message".
"More software projects have gone awry for lack of calendar time than for all other causes combined." -- Fred Brooks, Jr., _The Mythical Man Month_