Radiation Seed Therapy Is a Common Method for Treating Some $\mu$

Radiation seed therapy is a common method for treating some prostate cancers and brain tumors. Iodine-125 is one isotope used for this treatment. Iodine-125 decays with a half-life of 60 days by emitting X-rays with a photon energy of 27,000 eV. What mass of iodine-125 would have to be embedded in a 25 g tumor to produce a radiation dose of 125 Gy in 3 months' time (90 days) ? Note: 1 Gy = 1 J/kg, and 1 eV = 1.60 * 10^-19 J.

A) 0.37 $\mu$ g
B) 0.31 $\mu$ g
C) 0.10 $\mu$ g
D) 0.23 $\mu$ g
E) 0.16 $\mu$ g