MATH
posted by ROBIN .
A frustrated office worker throws his laptop out of his business’s highrise
office building. The height, h, in meters of the laptop above the ground at t
seconds can be modelled by
h(t)=125=1255t^2
Estimate the instantaneous rate at which the laptop hits the ground.

Where is there a highrise with windows that open?
Anyway  Graham has just answered your question.
http://www.jiskha.com/display.cgi?id=1374270782