user: Question: What is the average tonnage of the ship named Proletarij?
Columns: ['Date', 'Name of ship', 'Flag', 'Tonnage', 'Fate']
Types: ['text', 'text', 'text', 'real', 'text']
Sample row: ['5December1944', 'Proletarij', 'Soviet Union', 1123.0, 'sunk at']
SQL:

assistant: SELECT AVG("Tonnage") FROM "Table" WHERE "Name of ship" = 'Proletarij';