Iodine 131 is a radioisotope with a very short half-life of 8

Iodine 131 is a radioisotope with a very short half-life of 8.02 days,

making it highly radioactive. It is frequently used in small doses in thyroid cancer therapies. It has a biological half-life of 138 days. I-131 of 1 ?Ci is administered to a patient's thyroid of 20g. Assume that each I-131 decay release 0.23 MeV of beta-gamma energy, which is all absorbed by the thyroid.
(a)  Find its effective half-life tE.
(b)  Find its effective decay constant ?E.
(c)  Determine the effective number of I-131 atoms administered based on ?E.
(d) Determine the total dose (in Gy and rad) received by the organ for this treatment.