horizontal projectile motion physics problem

Question

A golfer hits a ball horizontally from a rooftop. It's in the air for about 1.8s before it lands on the street below. The distance from the side of the building to where it lands is 99m. How high is the roof?

Answer 1

given the ball is hit horizontally, the initial vertical velocity is zero

in the vertical direction, the ball is accelerated by the gravitational force at 9.8 m/sec²

h = 0.5gt² = 0.5 (9.8) (1.8)² =  15.87m