Question

I'm having a problem understanding a question. "If a man exerts a 200N force while pushing a crate 5.0 m across a floor against a frictional resistance of 40N, how much energy was expended by the person pushing?" I can figure out work done on the box and those sorts of questions but I don't get what is meant by how much energy is the man expending.
The work expended is the applied force (200 N) times the distance the crate moved (5.0 m). The amount of friction does not affect that result.
Thank you.

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