CREATE TABLE table_24620684_2 (us_national_average_electric_mix VARCHAR2, vehicle VARCHAR2)

When bmw activee is the vehicle type what is the u.s national average electric mix?
SELECT us_national_average_electric_mix FROM table_24620684_2 WHERE vehicle = "BMW ActiveE"
SELECT "us_national_average_electric_mix" FROM "table_24620684_2" WHERE "BMW ActiveE" = "vehicle"