Running a Quadratic Regression analysis on the data from floors 0-80, using matched-pair datapoints of (0; 14,000), (20; 7,000), (40; 3500), (60; 1750), & (80; 875) yields the following equation:
Floors 0-80
y= {[2.5 * (x^2)] + (-357.5 * x) + 13,725}
For 20-floor increments...
For x=20 we get 7,575 (75 ABOVE confirmed values)
For x=40 we get 3,425 (75 BELOW confirmed values)
For x=60 we get 1,275 (475 ABOVE confirmed values)
For x=80 we get 1,125 (250 ABVOE confirmed values)
For 10-floor increments NOT divisible by 20...
For x=10 we get 10,400 (100 BELOW formula value of 10,500)
For x=30 we get 5,250 (PRECISELY formula value of 5,250)
For x=50 we get 2,100 (525 BELOW formula value of 2,625)
For x=70 we get 950 (362 BELOW formula value of 1,312 {floored from 1,312.5})
Note that since the Floor 81-95 data follow a clear linear relationship, there is absolutely no point in even attempting to project a Quadratic Regression equation to them. However, if you're interested for OCD-related reasons, the equation is...
Floors 81-95
y= (-25x + 2875)
I have omitted the null-void [0 * (x^2)] statement from the above equation; the remaining equation is simply a linear equation in quadratic form, with a 100% fit to the data.