You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named [2-[(4-methoxy-4-oxobutyl)amino]-2-oxoethyl] 3-methylbenzo[g][1]benzofuran-2-carboxylate is given. What is its corresponding molecular formula?
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C21H21NO6
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