user: Question: Name the broadcast date for 7.4 viewers
Columns: ['Episode', 'Broadcast date', 'Run time', 'Viewers (in millions)', 'Archive']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['" Episode One "', '20May1972', '25:04', '7.6', 'PAL colour conversion']
SQL:

assistant: SELECT "Broadcast date" FROM "Table" WHERE "Viewers (in millions)" = '7.4';