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:
| Episode | Broadcast date | Run time | Viewers (in millions) | Archive |
| --- | --- | --- | --- | --- |
| " Episode 1 " | 3February1968 | 24:53 | 7.2 | 16mm t/r |
| " Episode 2 " | 10February1968 | 24:38 | 6.8 | 16mm t/r |
| " Episode 3 " | 17February1968 | 24:34 | 7.0 | Only stills and/or fragments exist |
| " Episode 4 " | 24February1968 | 24:50 | 8.4 | 16mm t/r |
| " Episode 5 " | 2March1968 | 24:19 | 8.0 | 16mm t/r |
| " Episode 6 " | 9March1968 | 24:41 | 8.3 | 16mm t/r |
Question:
what is all the  broadcast date when viewers were 8.4 millions
Answer:
1.0