Developing Binary Variables



I think I have this but I can 't get the Sumproduct to work



This gives me the correct answer if I have already determined Yield effects
of salt

Here Yield is a combination of production*Income already



Profit = Sumproduct (Area, Yield) - Sumproduct(Area,Costs)



Sumproduct(Area, Costs) = cost to produce

Sumproduct (Area, Yield) = return from production



What I need to do is alter the return from production to include the salt
impact within the function



Yield = Basic Yield - Threshold Impact * (Salt-Threshold)*Y



Where

Salt = level of salt in water

Threshold = salt level required to affect yield

Threshold Impact = impact of salt

Y = Dummy Binary Variable, which I then add as a constraint



But I have no idea how to put this into a Sumproduct formula to use in
Solver.



Sumproduct(Area, ?????)



Any suggestions would be greatly appreciated