Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Vehicle | Operating mode | EPA rated All-electric range | EPA rated combined fuel economy | Clean electric grid California (San Francisco) | U.S. national average electric mix | Dirty electric grid Rocky Mountains (Denver) |
| --- | --- | --- | --- | --- | --- | --- |
| Mitsubishi i-MiEV | All-electric | mi (km) | 112 mpg-e (30kW-hrs/100mi) | 100 g/mi (62 g/km) | 200 g/mi (124 g/km) | 290 g/mi (180 g/km) |
| Ford Focus Electric | All-electric | mi (km) | 105 mpg-e (32kW-hrs/100mi) | 110 g/mi (68 g/km) | 210 g/mi (131 g/km) | 310 g/mi (193 g/km) |
| BMW ActiveE | All-electric | mi (km) | 102 mpg-e (33kW-hrs/100mi) | 110 g/mi (68 g/km) | 220 g/mi (137 g/km) | 320 g/mi (199 g/km) |
| Nissan Leaf | All-electric | mi (km) | 99 mpg-e (34kW-hrs/100mi) | 120 g/mi (75 g/km) | 230 g/mi (143 g/km) | 330 g/mi (205 g/km) |
| Chevrolet Volt | Electricity only ( charge-depleting ) | mi (km) | 94 mpg-e (36kW-hrs/100mi) | 190 g/mi (118 g/km) (1) | 260 g/mi (162 g/km) (1) | 330 g/mi (205 g/km) (1) |
| Smart ED | All-electric | mi (km) | 87 mpg-e (39kW-hrs/100mi) | 130 g/mi (81 g/km) | 260 g/mi (162 g/km) | 380 g/mi (236 g/km) |
| Coda | All-electric | mi (km) | 73 mpg-e (46kW-hrs/100mi) | 160 g/mi (99 g/km) | 300 g/mi (186 g/km) | 440 g/mi (273 g/km) |
Question:
When bmw activee is the vehicle type what is the u.s national average electric mix?
Answer:
220 g/mi (137 g/km)