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 No. | Airdate | Total Viewers | Share | BBC One Weekly Ranking |
| --- | --- | --- | --- | --- |
| 1.0 | 8 April 2010 | 6700000.0 | 24.8% | 6.0 |
| 2.0 | 15 April 2010 | 5820000.0 | 20.8% | 11.0 |
| 3.0 | 22 April 2010 | 6367000.0 | 23.7% | 7.0 |
| 4.0 | 6 May 2010 | 5901000.0 | 22.6% | 10.0 |
| 5.0 | 13 May 2010 | 6751000.0 | 26.6% | 7.0 |
| 6.0 | 20 May 2010 | 6507000.0 | 26.2% | 7.0 |
Question:
What were the air-dates of the episodes before episode 4 that had a BBC One weekly ranking of 6?
Answer:
8 April 2010