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_57 (works_number INTEGER, builder VARCHAR, name VARCHAR)
### Question:
What is the average work number of Snowdon Ranger with the builder Vulcan Foundry?
### Answer:
SELECT AVG(works_number) FROM table_name_57 WHERE builder = "vulcan foundry" AND name = "snowdon ranger"