<Li> Laura Haddock as Megan Cantor (series 4) </Li> <Li> Patrick Malahide as George Cornelius (series 4) </Li> <Table> <Tr> <Th_colspan="2"> Series </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="2"> Originally aired </Th> </Tr> <Tr> <Th> First aired </Th> <Th> Last aired </Th> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 6 </Td> <Td_colspan="1"> 4 May 2010 (2010 - 05 - 04) </Td> <Td> 8 June 2010 (2010 - 06 - 08) </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> </Td> <Td_colspan="1"> 14 June 2011 (2011 - 06 - 14) </Td> <Td> 5 July 2011 (2011 - 07 - 05) </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> </Td> <Td_colspan="1"> 2 July 2013 (2013 - 07 - 02) </Td> <Td> 23 July 2013 (2013 - 07 - 23) </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> </Td> <Td_colspan="1"> 15 December 2015 (2015 - 12 - 15) </Td> <Td> 22 December 2015 (2015 - 12 - 22) </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Series </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="2"> Originally aired </Th> </Tr>

How many episodes are in luther season 4
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