Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Callsign | Area served | Frequency | Band | Freq currently | Purpose |
| --- | --- | --- | --- | --- | --- |
| 5AL | Alice Springs | 1530 | AM | 8AL (783 kHz) | National |
| 5DR | Darwin | 1500 | AM | see 8DR | National |
| 8DN | Darwin | 1242 | AM | 8TAB (HPON) | Commercial |
| 8DR | Darwin | 0 657 | AM | 8RN | National |
| 8KN | Katherine | 0 639 | AM | 8RN | National |
| 8TC | Tennant Creek | 0 684 | AM | 8RN | National |
Question:
What is the purpose for the katherine freq of 8rn?
Answer:
National