user: Question: What is the sum number of year when call of duty 4: modern warfare was the game?
Columns: ['Year', 'Game', 'Genre', 'Platform(s)', 'Developer(s)']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [2005.0, 'Resident Evil 4', 'Survival Horror : ( Third-Person ) Shooter', 'GameCube , PlayStation 2 Windows', 'Capcom']
SQL:

assistant: SELECT SUM("Year") FROM "Table" WHERE "Game" = 'call of duty 4: modern warfare';