CREATE TABLE table_9039 ("Plan" TEXT, "Downstream" TEXT, "Upstream" TEXT, "Up:Down Ratio" FLOAT, "Monthly Cap" TEXT, "Price" TEXT)

What is the highest up:down ratio with 4 mbit/s upstream?
SELECT MAX("Up:Down Ratio") FROM table_9039 WHERE "Upstream" = '4 mbit/s'
SELECT MAX("Up:Down Ratio") FROM "table_9039" WHERE "Upstream" = '4 mbit/s'