Question on Marx

I'm currently reading Capital Vol. 1 for an econ course and I have this question to answer, which I'm stuck on:



Q: For a firm to earn positive profits, what must the value added per worker-hour be relative to the value of labor-power?



I want to say the answer has something to do with absolute surplus value, probably somewhere in Ch. 9 for those with the book. But I'm confused at this point. :(



Any takers?

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