user: Question:  how many dbeingtrict with candidates being William B. Bankhead (D) 71.3% E. M. Reed (R) 28.7%
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Result', 'Candidates']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Alabama 1', 'Frank W. Boykin', 'Democratic', 1935.0, 'Re-elected', 'Frank W. Boykin (D) Unopposed']
SQL:

assistant: SELECT COUNT("District") FROM "Table" WHERE "Candidates" = 'William B. Bankhead (D) 71.3% E. M. Reed (R) 28.7%';