The following data were obtained from experiments to find the molecular formula of lidocaine, a local anesthetic, which contains only carbon, hydrogen, nitrogen, and oxygen. Complete combustion of a 3.54-{\rm g} sample of lidocaine with excess {\rm{O}}_2 formed 9.32 g {\rm{CO}}_2 and 3.00 g {\rm{H}}_2 {\rm{O}}. Another sample of mass 2.35 {\rm g} was found to contain 0.281 g of {\rm N}. The molar mass of lidocaine was found to be 234. Find the molar formula of lidocaine.