CREATE TABLE table_64345 ("Class" TEXT, "Railway number ( s ) " TEXT, "Quantity" FLOAT, "Year ( s )  of manufacture" TEXT, "Type" TEXT)

Which Year(s) of manufacture has a Quantity of 2, and a Type of b n2t?
SELECT "Year(s) of manufacture" FROM table_64345 WHERE "Quantity" = '2' AND "Type" = 'b n2t'
SELECT "Year(s) of manufacture" FROM "table_64345" WHERE "Quantity" = '2' AND "Type" = 'b n2t'