You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
sodium;2-[3-(2-hydroxyethyl)-2-octyl-4,5-dihydroimidazol-1-ium-1-yl]acetate;hydroxide is the IUPAC name of a molecule. Please give its molecular formula.
user
C15H29N2NaO4
assistant