user: Question: What is the region 1 date for series 4
Columns: ['Series', 'Episodes', 'Series premiere', 'Series finale', 'Region 1', 'Region 2', 'Region 4']
Types: ['text', 'real', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Pilot', 1.0, '18 February 2008', '18 February 2008', 'N/A', 'N/A', 'N/A']
SQL:

assistant: SELECT "Region 1" FROM "Table" WHERE "Series" = '4';