if a sample of the radioactive nuclide 139cs has an activity of 0.0730 ci, what is the instantaneous rate of decomposition of 139cs in terms of grams per second? the mass of 139cs is 138.9134 amu. 1 ci 3.700 × 1010 disintegrations/ s, 1 amu 1.66054 ×10–24 g