Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_23840623_4 ( dirty_electric_grid_rocky_mountains__denver_ VARCHAR, clean_electric_grid_california__san_francisco_ VARCHAR )

### Question ###
What is the dirty electric grid rocky mountains (denver) for the vehicle with the clean electric grid california (san francisco) of 160 g/mi (99 g/km)?

### Accurate SQL ###

SELECT dirty_electric_grid_rocky_mountains__denver_ FROM table_23840623_4 WHERE clean_electric_grid_california__san_francisco_ = "160 g/mi (99 g/km)"