A radioactive tracer is added to water flowing through a treatment channel. A detector follows the tracer during an 8-hour survey. The tracer must have an activity of at least 300 Bq at the end of the survey and an activity of no more than one tenth of its initial activity 24 hours after the survey starts. Both candidate tracers have an initial activity of 1600 Bq.
| Tracer | Half-life |
|---|---|
| P | 4 hours |
| Q | 8 hours |
Which tracer should be used? Calculate the activity of each tracer at the end of the survey and 24 hours after the survey starts to support your answer.