Rocket trajectory in vertical launch then free fall

[jontyjashan]

Homework Statement

A rocket is launched to travel vertically upward with a constant velocity of say...20 m/s.After
travelling maybe 35 s the rocket develops snag and its fuel supply is cut off. the rocket then travels like a free body, the height achieved by the rocket will be

Homework Equations

displacement=velocity *time

The Attempt at a Solution

20 *35=700m

this is not the answer why?

 

[drizzle]

you add to that the extra displacement the rocket travels as a free body till the point where its velocity reachs [0 m/s]