Hello everyone!
I'm trying to make this, but don't know:

We have:
Amount of money: 1000 (changeable)
Beginning # of units: 0,1 (changeable)
Delta: 200 (changeable)
Rate of decrease: 50% (changeable)

0,1 unit should be added for every 200$ increase of the sum
(1000+200=1200; 1200+200=1400; 1400+500=1900; 1900+256=2156 etc)
0,1 unit should be taken away after decreasing by100$ (because the rate
of decrease = 50% (changeable))

After increasing of 1000 + 200, quantity of units should also increase
for 0,1, so it should be 0,2 (1200), 0,3(1400), 0,4(1600)..... Amount
of money can increase not only by 200, but for any sum. If that sum is
(for example) 500, we should increase by 0,2 etc.

But when this some decreasing we are using rate of decrease (for
example 50%, (changeable):
0,4 units - 1600
0,3 units - 1500
0,2 units - 1400
0,1 unit - 1300

I'll be appreciate for any help!
Alex Vasyuta