user: Question: Which Year(s) of manufacture has a Quantity of 2, and a Type of B n2t?
Columns: ['Class', 'Railway number(s)', 'Quantity', 'Year(s) of manufacture', 'Type']
Types: ['text', 'text', 'real', 'text', 'text']
Sample row: ['B(Krauss) ( de )', '172–177', 6.0, '1867–1868', 'B n2t']
SQL:

assistant: SELECT "Year(s) of manufacture" FROM "Table" WHERE "Quantity" = 2.0 AND "Type" = 'B n2t';