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_50 ( quantity INTEGER, type VARCHAR, retired VARCHAR )

### Question ###
What is the lowest quantity of the 1b n2 type, which was retired in 1907-12?

### Accurate SQL ###

SELECT MIN(quantity) FROM table_name_50 WHERE type = "1b n2" AND retired = "1907-12"