user: Question: What is the smallest amount of freight carried on the road that closed on march 31 and reached super B capacity on february 17 after 2011?
Columns: ['Year', 'Road Opened', 'Road Closed', 'Freight Carried s Tonne', 'Super B Capacity Reached [ citation needed ]', 'Number of Truck Loads North']
Types: ['real', 'text', 'text', 'real', 'text', 'real']
Sample row: [2000.0, 'January 29', 'April 3', 111090.0, 'n/a', 3703.0]
SQL:

assistant: SELECT MIN("Freight Carried s Tonne") FROM "Table" WHERE "Road Closed" = 'march 31' AND "Super B Capacity Reached [ citation needed ]" = 'february 17' AND "Year" > 2011.0;