A large dataset contains records of cycle-hire journeys. An extract is shown below.
| Record | Start time | End time | Distance (km) | Station code |
|---|---|---|---|---|
| 1 | 08:14 | 08:31 | 4.2 | BT01 |
| 2 | 09:05 | — | 3.8 | BT03 |
| 3 | 10:22 | 10:18 | 1.6 | BT02 |
| 4 | 11:40 | 11:55 | 42.7 | BT-01 |
| 5 | 08:14 | 08:31 | 4.2 | BT01 |
Identify four possible data-quality problems in the extract.
For any two of the problems, describe an appropriate action before analysis.