user: Question: On broadcast date is 21March1970, how many people tuned in?
Columns: ['Episode', 'Broadcast date', 'Run time', 'Viewers (in millions)', 'Archive']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['" Episode 1 "', '21March1970', '24:33', '7.1', 'PAL 2" colour videotape']
SQL:

assistant: SELECT SUM("Viewers (in millions)") FROM "Table" WHERE "Broadcast date" = '21March1970';