You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named [(4aS,5R,6R,7S,8aR,9aS)-7-hydroxy-3,4a,5-trimethyl-2-oxo-4,5,6,7,8,8a,9,9a-octahydrobenzo[f][1]benzofuran-6-yl] (E)-3-methylpent-2-enoate by IUPAC nomenclature, provide its molecular formula.
user
C21H30O5
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