The greatest concentration of iodine in the body is in the thyroid gland, so radioactive iodine-131 is often used as a tracer to help diagnose thyroid problems. Suppose the activity of 131I in a patient’s thyroid is initially 1.85 × 10⁶ Bq. 131I decays via beta radiation with an average energy of 180 keV per decay. Calculate the absorbed dose in sieverts the patient’s thyroid receives in the first hour of exposure. Assume that half of the radiation is absorbed by the thyroid gland, which has a mass of 150 g.