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 | Viewers | BBC Three weekly ranking | Cable rank |
| --- | --- | --- | --- | --- |
| 1.0 | 25 March 2010 | 862000.0 | 3 | 13 |
| 2.0 | 1 April 2010 | 1067000.0 | 4 | 11 |
| 3.0 | 8 April 2010 | 1115000.0 | 1 | 2 |
| 4.0 | 15 April 2010 | 1021000.0 | 2 | 8 |
| 5.0 | 22 April 2010 | 910000.0 | 4 | 17 |
| 6.0 | 29 April 2010 | 885000.0 | 5 | 12 |
| 7.0 | 6 May 2010 | 569000.0 | N/A | N/A |
Question:
What episode number had a cable ranking of 8?
Answer:
4.0