Scale building ground area by distance

Hello :)

I am new to grasshopper and having some problems, hope you can help!

I've created a city with urban places and i want to scale the dimensions of the buildings ground area in order to their distance to the three urban places. 

So, when the buildings is far away from the circles, they need to get a larger ground area and when they are closer: smaller ground area. 

I did the same with the height of the buildings, but i just can't figure it out with the ground areas. 

I really hope you can help! :)