user: Question: How many districts have an incumbent first elected in 1940?
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Result', 'Candidates']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Florida 1', 'J. Hardin Peterson', 'Democratic', 1932.0, 'Re-elected', 'J. Hardin Peterson (D) Unopposed']
SQL:

assistant: SELECT COUNT("District") FROM "Table" WHERE "First elected" = 1940.0;