Table:
text: List of Last of the Summer Wine episodes
Series
Series
Series_Number Number_of_Episodes Original_Air_Date DVD_Region_2_release_date DVD_Region_1_release_date
12 10 1990 26 December 2008 12 July 2011
13 6 1991 26 December 2008 21 February 2012
14 9 1992 26 October 2009 17 April 2012
15 9 1993 26 October 2009 24 July 2012
16 8 1995 27 December 2010 TBA
17 10 1995 27 December 2010 15 June 2004
18 10 1997 7 February 2011 15 January 2013
19 10 1998 7 February 2011 16 April 2013
20 10 1999 26 March 2012 9 July 2013
21 10 2000 26 March 2012 15 October 2013
22 10 2001 23 April 2012 14 January 2014
23 10 2002 23 April 2012 TBA
24 10 2003 TBA TBA

Question: From the Last of the Summer Wine episodes list, what is the sum of the number of episodes that originally aired after 1991 with a serial number less than 21 and a DVD Region 2 release date of March 26, 2012?