Answer;
= 60 m
Explanation;
s = 80 m
= ½at² = ½ * 9.8m/s² * t² → t = 4.04 s
At any time 0 ≤ t ≤ 4.04 s, height is
y = Yo + ½at² = 80 m - 4.9m/s² * t²
so at t = 4.04s/2 = 2.02 s,
y = 80 m - 4.9m/s² * (2.02s)² = 60 m
(so it drops 15 m during the first 2.02 s and 60 m during the second 2.02 s)