Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_name_73 (entered_service INTEGER, builder VARCHAR, number VARCHAR)
### Question:
When did the tom smith built train enter service with a number under 7007?
### Answer:
SELECT AVG(entered_service) FROM table_name_73 WHERE builder = "tom smith" AND number < 7007