Motion in a Plane

The maximum speed of a boat in still water is 27‌km∕h. Now this boat is moving downstream in a river flowing at 9‌km∕h. A man in the boat throws a ball vertically upwards with speed of 10m∕ s. Range of the ball as observed by an observer at rest on the river bank, is ______ cm.(. Take g=10m∕ s2)