It would be easier if you show the steps that you've used to come up with that number and what is the value for g that you have used in your calculation.

You would need to find out how high the ball will get based on the launch parameters. It's not going straight up so you will need to use trigonometry to get the vertical component of the velocity. This information will provide the time it takes for the ball to go up and stop and the additional vertical distance traveled upward from the top of the building. With the new height and the height of the building, figure out how long it takes for the ball to fall to the ground. Add the time for the ball to go up and stop and the time to fall from its new height to get the total travel time.