Date and such given in the thread above. And I really couldn't care less about a challenge, anyway. It's a useless number.
Data is also capable of learning. Have you ever seen him scanning through data files at an incomprehensible speed?Would Spock be smarter since he can always learn more whereas Data would be obsolete by the end of the year and replaced by Data 2.0. Or else he would have to have service packs every month to keep up with all the new updates.
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Data also has to be programmed by someone like Spock. At some point Data's brain would be no smarter than a watch.