Optimization problem - I need a flat floor!

#1
Okay, so my concrete floor is not level - there are high spots and there are low spots. My goal is to achieve <1/8th inch difference between any two spots within any 10 foot radius. What I have is elevation measurements across the entire floor, at every 6 inches along the Y and the X axis.

Initially, I created a program to find any difference between any two spots that is greater than 1/8th of an inch and less than or equal to 10 ft apart. But then I realized if I were to shave down the high spot, I may create another difference between some other two spots.

How can find the optimal solution? How can I figure out which spots to shave down or which gaps to fill in such that I can achieve the desired flatness with the least amount of work?