Calculate the molar mass of the noble gas krypton in a natural sample, which is 0.62% 78Kr (molar mass 77.92 g/mol), 2.1% 80Kr (molar mass 79.91 g/mol), 10.62% 82Kr (molar mass 81.91 g/mol), 11.73% 83Kr (molar mass 82.92 g/mol), 57.72% 84Kr (molar mass 83.91 g/mol), and 17.21% 86Kr (molar mass 85.91 g/mol). Answer in units of g/mol. Your answer must be within ± 0.001%