CREATE TABLE "builders_and_numbering" (
  "year" real,
  "quantity" real,
  "manufacturer" text,
  "serial_number" text,
  "tvr_numbers" text,
  "gwr_numbers" text
);

Question: What is the average Year that has a Quantity of 10, and a GWR Numbers of 409, 290, 315, 317–321, 324, 333?
SQL: SELECT AVG("year") FROM "builders_and_numbering" WHERE "quantity"=10 AND "gwr_numbers"='409, 290, 315, 317–321, 324, 333';