Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_name_97 (tonnage INTEGER, nationality VARCHAR, name_of_ship VARCHAR)
### Question:
What was the average tonnage for the Siljan ship from Sweden?
### Answer:
SELECT AVG(tonnage) FROM table_name_97 WHERE nationality = "sweden" AND name_of_ship = "siljan"