You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(9bR)-6-acetyl-7,9-dihydroxy-8,9b-dimethyl-2-[1-(2,3,4,9-tetrahydro-1H-carbazol-1-ylamino)ethylidene]dibenzofuran-1,3-dione is the IUPAC name of a molecule. Please give its molecular formula.
user
C30H28N2O6
assistant