CREATE TABLE table_40950 ("Year" FLOAT, "Date" TEXT, "Television" TEXT, "Designated Visitors" TEXT, "Designated Home" TEXT, "Stadium" TEXT, "City" TEXT)

What year had a date of TBA where the Oakland raiders were the home team?
SELECT AVG("Year") FROM table_40950 WHERE "Date" = 'tba' AND "Designated Home" = 'oakland raiders'
SELECT AVG("Year") FROM "table_40950" WHERE "Date" = 'tba' AND "Designated Home" = 'oakland raiders'