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_80 (year INTEGER, date VARCHAR, designated_home VARCHAR)
### Question:
What year had a date of TBA where the Oakland raiders were the home team?
### Answer:
SELECT AVG(year) FROM table_name_80 WHERE date = "tba" AND designated_home = "oakland raiders"