The radioactive nuclide 99Tc can be injected into a patient's bloodstream in order to monitor the blood flow, measure the blood volume, or find a tumor, among other goals. The nuclide is produced in a hospital by a "cow" containing 99Mo, a radioactive nuclide that decays to 99Tc with a half-life of 67 h. Once a day, the cow is "milked" for its 99T, which is produced in an excited state by the 99Mo; the 99Tc de-excites to its lowest energy state by emitting a gamma-ray photon, which is recorded by detectors placed around the patient. The de-excitation has a half-life of 6.0 h.

(a) By what process does 99Mo decay to 99Tc?

(b) If a patient is injected with an 8.2 x 107 Bq sample of 99Tc, how many gamma-ray photons are initially produced within the patient each second?

(c) If the emission rate of gamma-ray photons from a small tumor that has collected 99Tc is 38 per second at a certain time, how many excited-states 99Tc are located in the tumor at that time?