The height of a falling object can be approximated (assuming no air resistance) by
h(t) = -16t^2 + h0
where h0 is the initial height of the object.
We are given h(5.6) = 0 and are asked to find h0.
0 = -165.6^2 + h0
165.6^2 = h0
501.76 = h0
The height of the building is about 500 ft.