You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the molecule identified by 12-benzoyl-4-methoxy-9-methyl-8-oxa-10-azatricyclo[7.3.1.02,7]trideca-2(7),3,5-trien-11-one ?
user
C20H19NO4
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