user: Question: what is the tonnage grt of the ship Author?
Columns: ['Date', 'Ship', 'Type', 'Nationality', 'Tonnage GRT']
Types: ['text', 'text', 'text', 'text', 'real']
Sample row: ['11 Jan 16', 'Corbridge', 'Cargo ship', 'United Kingdom', 3687.0]
SQL:

assistant: SELECT "Tonnage GRT" FROM "Table" WHERE "Ship" = 'Author';