CREATE TABLE table_16105186_2 (us_national_average_electric_mix VARCHAR2, midwest__des_moines_ VARCHAR2)

What was the US national average electric mix rating for the vehicle that was rated 280 g/mi (174 g/km) in the Midwest?
SELECT us_national_average_electric_mix FROM table_16105186_2 WHERE midwest__des_moines_ = "280 g/mi (174 g/km)"
SELECT "us_national_average_electric_mix" FROM "table_16105186_2" WHERE "280 g/mi (174 g/km)" = "midwest__des_moines_"