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Below are the choices that can be found from other sources:
A. 90 chairs/worker/day
B. 20 chairs/worker/day
C. 15 chairs/worker/day
D. 75 chairs/worker/day
E. 60 chairs/worker/day
The answer is C. 15 chairs/worker/day. Divide the output of 450 chairs by the inputs of 30 worker-days.