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_72 (up INTEGER, upstream VARCHAR)
### Question:
What is the highest up:down ratio with 4 mbit/s upstream?
### Answer:
SELECT MAX(up) AS :down_ratio FROM table_name_72 WHERE upstream = "4 mbit/s"