A 70-kg patient is to be given a medical test involving the ingestion of 99m/43 Tc which decays by emitting a 140-keV gamma. The half-life for this decay is 6 hours. Assuming that about half the gamma photons exit the body without interacting with anything, what must be the initial activity of the Tc sample if the whole-body dose cannot exceed 50mrem? Make the rough approximation that biological elimination of Tc can be ignored.