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_40 ( laps INTEGER, time_retired VARCHAR, grid VARCHAR )

### Question ###
In grid 15, how many laps were there before ending with a time of exhaust?

### Accurate SQL ###

SELECT SUM(laps) FROM table_name_40 WHERE time_retired = "exhaust" AND grid < 15