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:
| Series Number | Number of Episodes | Original Air Date | DVD Region 2 release date | DVD Region 1 release date |
| --- | --- | --- | --- | --- |
| 1.0 | 6.0 | 1973.0 | 2 September 2002 | TBA |
| 2.0 | 7.0 | 1975.0 | 2 September 2002 | TBA |
| 3.0 | 7.0 | 1976.0 | 26 July 2004 | 11 March 2008 |
| 4.0 | 7.0 | 1977.0 | 26 July 2004 | 9 September 2008 |
| 5.0 | 7.0 | 1979.0 | 5 March 2007 | 6 September 2009 |
| 6.0 | 7.0 | 1982.0 | 5 March 2007 | 27 April 2010 |
| 7.0 | 6.0 | 1983.0 | 3 March 2008 | 27 April 2010 |
| 8.0 | 6.0 | 1985.0 | 3 March 2008 | 9 July 2010 |
| 9.0 | 12.0 | 1987.0 | 5 May 2008* | 18 January 2011 |
| 10.0 | 6.0 | 1988.0 | 22 September 2008 | 12 April 2011 |
| 11.0 | 7.0 | 1989.0 | 22 September 2008 | 12 April 2011 |
| 12.0 | 10.0 | 1990.0 | 26 December 2008 | 12 July 2011 |
| 13.0 | 6.0 | 1991.0 | 26 December 2008 | 21 February 2012 |
| 14.0 | 9.0 | 1992.0 | 26 October 2009 | 17 April 2012 |
| 15.0 | 9.0 | 1993.0 | 26 October 2009 | 24 July 2012 |
| 16.0 | 8.0 | 1995.0 | 27 December 2010 | TBA |
| 17.0 | 10.0 | 1995.0 | 27 December 2010 | 15 June 2004 |
| 18.0 | 10.0 | 1997.0 | 7 February 2011 | 15 January 2013 |
| 19.0 | 10.0 | 1998.0 | 7 February 2011 | 16 April 2013 |
| 20.0 | 10.0 | 1999.0 | 26 March 2012 | 9 July 2013 |
| 21.0 | 10.0 | 2000.0 | 26 March 2012 | 15 October 2013 |
| 22.0 | 10.0 | 2001.0 | 23 April 2012 | 14 January 2014 |
| 23.0 | 10.0 | 2002.0 | 23 April 2012 | TBA |
| 24.0 | 10.0 | 2003.0 | TBA | TBA |
| 25.0 | 10.0 | 2004.0 | TBA | TBA |
| 26.0 | 10.0 | 2005.0 | TBA | TBA |
| 27.0 | 9.0 | 2006.0 | TBA | TBA |
| 28.0 | 10.0 | 2007.0 | TBA | TBA |
| 29.0 | 11.0 | 2008.0 | TBA | TBA |
| 30.0 | 10.0 | 2009.0 | TBA | TBA |
| 31.0 | 6.0 | 2010.0 | TBA | TBA |
Question:
What was the original air date of series number 10?
Answer:
1988.0