Cerium, Holmium, Nitrogen, you would have the molar mass of each element, and multiply it by that number of atoms.
Cerium = 140.116 * 1 = 140.116
Holmium = 164.93032 * 1 = 164.93032
Nitrogen = 14.0067 * 1 = 14.007
now you add it all together, and get your answer, which is 319.05332
Hope this helps you out!
