Figure 1 shows how the activity of two radioactive medical tracers, Tracer A and Tracer B, changes with time inside a patient's body.
| Time (hours) | Activity of Tracer A (MBq) | Activity of Tracer B (MBq) |
|---|---|---|
| 0 | 1200 | 1200 |
| 3 | 1009 | 849 |
| 6 | 849 | 600 |
| 9 | 714 | 424 |
| 12 | 600 | 300 |
| 15 | 505 | 212 |
| 18 | 424 | 150 |
Use the data in Figure 1 to determine the half-life of Tracer B.