Table schema:
CREATE TABLE table_name_96 (year INTEGER, release_air_date VARCHAR, role VARCHAR, radio_station_production_company VARCHAR)

Question: Role of narrator, and a Radio Station/Production Company of bbc audiobooks, and a Release/Air Date of 13 november 2008 is what sum of the year?
SQL: SELECT SUM(year) FROM table_name_96 WHERE role = "narrator" AND radio_station_production_company = "bbc audiobooks" AND release_air_date = "13 november 2008"