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 | Original title | Directed by | Written by | Original airdate | Duration | Viewership |
| --- | --- | --- | --- | --- | --- | --- |
| 16.0 | " But is it Art? " | Dewi Humphreys | Jim Sullivan | 2November2007 | 30 minutes | 5.34 million |
| 17.0 | " The Lonely Herdsman " | Dewi Humphreys | Jim Sullivan | 9November2007 | 30 minutes | 4.62 million |
| 18.0 | " If You Go Down to the Woods " | Dewi Humphreys | Jim Sullivan | 23November2007 | 30 minutes | 5.20 million |
| 19.0 | " Sweet Sorrow " | Dewi Humphreys | John Sullivan and Keith Lindsay | 30November2007 | 30 minutes | 6.05 million |
| 20.0 | " Fifteen Minutes " | Dewi Humphreys | David Cantor | 7December2007 | 30 minutes | 5.08 million |
| 21.0 | " The Final Curtain " | Dewi Humphreys | John Sullivan | 14December2007 | 30 minutes | 5.46 million |
Question:
Name the total number of episodes written by david cantor
Answer:
1.0