user: Question: Which Year is the lowest when the Viewers are 13.7 million?
Columns: ['Year', 'Network', 'Lap-by-lap', 's Color commentator', 'Pre-Race Host', 'Pre-Race Analyst(s)', 'Ratings', 'Viewers']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [2007.0, 'Fox', 'Mike Joy', 'Darrell Waltrip Larry McReynolds', 'Chris Myers', 'Jeff Hammond Darrell Waltrip', '10.1/20', '17.5 million']
SQL:

assistant: SELECT MIN("Year") FROM "Table" WHERE "Viewers" = '13.7 million';