we have 2 right angled triangles here , with one of the acute angles equal, because the angle of incidence of the reflection in the pool equals the angle of reflection.
The triangles are similar so we can say
1 / h = 0.5 / 74 ( the 74 comes from 74.5 - 0.5)
h = 74 / 0.5 = 148m
height of the building is about 148 m.
