Iodine-123 is a radioactive isotope used in medicine to test the function of the thyroid gland. If a 350 - microcurie (µCi) dose of iodine-123 is administered to a patient, the quantity Q left in the body after t hours is approximately Q = 350(1/2)^t/13.1.

a. How long does it take for the level of iodine-123 to drop to 10 µCi?

b. Find the rate of change of the quantity of iodine-123 at 12 hr, 1 day, and 2 days. What do your answers say about the rate at which iodine decreases as time increases?