A medical radiotherapy source contains Iodine-131 (53131I^{131}_{53}\text{I}53131I), which has a half-life of 8.0 days8.0\text{ days}8.0 days. Initially, the activity of the Iodine-131 in the source is 3.6×108 Bq3.6 \times 10^8\text{ Bq}3.6×108 Bq.
What is the number of Iodine-131 nuclei remaining in the source after exactly 24 days24\text{ days}24 days?
4.5×1074.5 \times 10^74.5×107
5.2×1085.2 \times 10^85.2×108
4.5×10134.5 \times 10^{13}4.5×1013
6.0×10136.0 \times 10^{13}6.0×1013
