Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_73 ( tonnage INTEGER, type_of_ship VARCHAR, date_entered_service VARCHAR )

### Question ###
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?

### Accurate SQL ###

SELECT SUM(tonnage) FROM table_name_73 WHERE type_of_ship = "twin screw ro-ro motorship" AND date_entered_service = "11 february 1983"