Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
what is the sum of tonnage when the type of ship is twin screw ro-ro motorship and the date entered service is 11 february 1983?

### Inputs:
table_name: table, columns: ["Ship's name", 'Date entered service', 'Date withdrawn', 'Tonnage', 'Type of Ship']

### Response:
SELECT SUM Tonnage FROM table WHERE Type of Ship = twin screw ro-ro motorship AND Date entered service = 11 february 1983