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Please use [code][/code] tags around your code to maintain format and readability.
1. I presume the awk is inside another script? What language is it?
2. Are you allowing the user to only enter part of the author and/or title? If so, your solution will currently output multiple entries.
3. $sold needs to be passed to awk the same as $title and $author
4. Used in this way, awk will not update anything and simply output information
5. You subtract $sold from the fifth field, but this is the Sold field ... shouldn't this be an addition? (as per the end of your post)