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_name_60 (laps INTEGER, time_retired VARCHAR, driver VARCHAR)

### Question ###
What is the mean number of laps when time/retired was spun off and the driver was Nick Heidfeld?

### Accurate SQL ###

SELECT AVG(laps) FROM table_name_60 WHERE time_retired = "spun off" AND driver = "nick heidfeld"