Nicotinamide is a water-soluble vitamin important in metabolism. A deficiency in this vitamin results in the debilitating condition known as pellagra. Nicotinamide is 59.0% C, 5.0% H, 22.9% N, 13.1% O, by mass. Addition of 3.88 g of nicotinamide to 30.0 mL nitrobenzene, C6H5NO2 (d = 1.204 g/mL), lowers the freezing point from 5.7 to -1.4 °C. What is the molecular formula of this compound?