user: ### NOW ANSWER:
Question: What is the highest up:down ratio with 4 Mbit/s upstream?
Columns: ['Plan', 'Downstream', 'Upstream', 'Up:Down Ratio', 'Monthly Cap', 'Price']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Internet Popular', '512 kb/s', '256 kbit/s', 0.5, '10 GB', 'R$ 29,80']
SQL:

assistant: SELECT MAX("Up:Down Ratio") FROM "Table" WHERE "Upstream" = '4 Mbit/s';