Answer: The rock would still weigh 90lbs
Explanation:
No, weight has being proven to reduce by the further you move from the center of the Earth. But since even the tallest buildings in the world or tallest mountains are a tiny fraction of the Earth’s radius, the difference in weight won’t be something that can be measured as it’s a tiny fraction. So the mass of the rock doesn’t change what changes is the gravitational force ( g ). So the rock would still end up weighing 90lbs even at the top of the tower because it is still within the earths atmosphere.