SCHEMA:
CREATE TABLE table_name_49 (year INTEGER, quantity VARCHAR, gwr_numbers VARCHAR)
USER:
What is the average Year that has a Quantity of 10, and a GWR Numbers of 409, 290, 315, 317–321, 324, 333?

QUERY:
SELECT AVG(year) FROM table_name_49 WHERE quantity = 10 AND gwr_numbers = "409, 290, 315, 317–321, 324, 333"