Table schema:
CREATE TABLE table_name_2 (year VARCHAR, numbers__quantity_ordered_ VARCHAR, fuel_propulsion VARCHAR, length VARCHAR)

Question: 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)"