Calculate the molar mass of the noble gas krypton in a natural sample, which is 0.84% 78 Kr (molar mass 77.92 g/mol), 2.2% 80 Kr (molar mass 79.91 g/mol), 11.23% 82 Kr (mo-lar mass 81.91 g/mol), 11.59% 83 Kr (molar mass 82.92 g/mol), 56.72% 84 Kr (molar mass 83.91 g/mol), and 17.42% 86 Kr (molar mass 85.91 g/mol). Answer in units of g/mol.