The atomic mass of cobalt
It is given that Cyanocobalamin (vitamin B12) is commonly found in vitamin supplements. It contains 4.34% cobalt by mass and there is one atom of cobalt in every molecule of cyanocobalamin
So the mass of Cyanocobalamin which contains 1 g atom or 59 g Cobalt represents its molar mas.
So molar mass of Cyanocobalamin