CREATE TABLE table_name_2 (year VARCHAR(255), numbers__quantity_ordered_ VARCHAR(255), fuel_propulsion VARCHAR(255), length VARCHAR(255))
What year was the diesel fuel propulsion, with a length of 40', and numbers (quanity ordered) of 3701-3729 (29 buses), retired?
    
SQL: SELECT year AS Retired FROM table_name_2 WHERE fuel_propulsion = "diesel" AND length = "40'" AND numbers__quantity_ordered_ = "3701-3729 (29 buses)"