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(R)=(400+20R)(90-R)36000-400R+1800-20R^236000+1400R-20R^2
We move all terms to the left:
(R)-((400+20R)(90-R)36000-400R+1800-20R^236000+1400R-20R^2)=0
We do not support eRpression: R^236000
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