Nested if/or function with three conditions

Hello everyone. Let me start by saying that there's a bit of background information with what I'm doing and what I'm trying to do, so I'll explain the situation the best I can and if something needs to be elaborated on, I can do so.


What I'm trying to do is create a spreadsheet that will predict the rate of decline of water produced from an oil well in a particular area. When a well first starts pumping, a given amount of water comes out in a day. Over time, the amount of water that comes out decreases gradually, almost like a decay curve. The spreadsheet I'm making will take data from a specific square of land, or township (to be selected from a drop down list), and predict the quantity of water that will be produced on a certain day after a well comes online. This prediction is done by taking two coefficients, A and B, and plugging them into an equation that's specific for that township. Each township has a different value for the A and B coefficients, the values of which are pulled from a different sheet using VLOOKUP after a specific township is selected from the list.


Most of these townships fit one equation: A + B*ln(0.033) (Let's call it equation 1). The townships that fit this equation I'm going to refer to as group 1.

Two other townships fit a unique equation: exp(A + B*exp(-.033)) (Equation 2). These will be Group 2 townships.

And one township fits equation: A/(1+ A*B*0.033) (Equation 3)


Previously, I only had to work with Groups 1 and 2. This was easy enough, and I had used the cell formula:

=IF(OR($B$4="17 27N 8W",$B$4="17 28N 8W"),EXP(B8+B9*EXP(-0.033)),B8+B9*LN(0.033))

Where B4 is the Township name that specifies that if the township selected belongs in Group 2, you would use Equation 2. If otherwise, you would use Equation 1. B8 and B9 are the A and B coefficients, respectively.


What I would like to do now is add in a third condition that says that if the lone township that fits Equation 3 is selected, that equation will be used instead of the other two. I've tried simply adding in that condition to what I already have, and have also tried to do a simple nested IF function with the three conditions, but I'm always getting an error message that says I have too many arguments. If there is any advice you can give, I'd appreciate it, as I'm not too Excel savvy when it comes to anything beyond simple cell formulas.

Please let me know if I need to attach any more details and I will do the best I can.

Works like a charm! Thank you so much!