excluding sums outside of a calculated range using "if" function

[Harvest Moon]

I am trying to set up a table that will calculate tiered costs for water. Using total consumption, I need to break down the tiers and not have any negative results show. Example: total consumption is 50,000 units. First 2,000 are charged at $2.00; next 7,000 are charged at $3.00, next 9,000 are charged at $4.00. I am attempting to specify, for instance, "if TOTAL > 9,000 and < 18,000, subtract 9,000 from the total; if TOTAL < 9,000, enter 0, if TOTAL > 18,000, enter 9,000. I can't seem to get the syntax right.
My current formula attempt is "IF(D4>900<1800,D4-9000,IF(D4>18000,9000,IF(D4-9000<0,0)))" where D4=12,100. I keep getting zero for the answer, which should be 3,100. I have been working on this long enough to believe that I am missing something very simple. If anyone can correct me, I will be overjoyed.
Thank you in advance!!!

[Kevin UK]

Hi Harvest Moon

Perhaps the VLOOKUP function might be worth looking into.

VLOOKUP function.

[Harvest Moon]

I am either dumber than I thought, or more frazzled. I cannot wrap my head around the VLOOKUP formula and make it work for my application. Thank you for the suggestion, though; I think I may stop here, let it percolate, and get a fresh start next week. Sometimes that actually works!
Thanks again,
HM