user: Question: On what Date is the Winning Score 71-69-68-70=278?
Columns: ['Date', 'Tournament', 'Winning score', 'To par', 'Margin of victory']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Feb 11, 1978', 'Bob Hope Desert Classic', '69-67-67-67-69=339', '−21', '2 strokes']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Winning score" = '71-69-68-70=278';