user: Question: When was the rate for 16-17 year olds £3.40?
Columns: ['From', 'Adult Rate', 'Development Rate', '16-17 Year Olds Rate', 'Apprentice Rate']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['1 Oct 2013', '£6.31', '£5.03', '£3.72', '£2.68']
SQL:

assistant: SELECT "From" FROM "Table" WHERE "16-17 Year Olds Rate" = '£3.40';