Solver problem

[Damien Bancal]

Hello

 I’m trying to use the solver to solve a problem at work.

My problem : I have product with 3 years lifespan. I know how much have been sold each year to a list of clients and how much they have now and I’m trying to find the yearly average survival rate of my product (percentage of the products sold in year XXXX which are still working). Once translated in an equation with 3 clients (named A to C).

X the number of item sold (XA12 : number of item sold in 2012 to client A) => known value.

S the survival rate (S12 the survival rate for the item sold in 2012, S11 for whose sold in 2011 and so on) => unknow value.

P the population (PA Product population client A, PB for client B and so on) => known values.

XA12*S12+XA11*S11+XA10*S10=PA

XB12*S12+XB11*S11+XB10*S10=PB

XC12*S12+XC11*S11+XC10*S10=PC

I want to put limit to the potential value of them. For example, I know that the survival rate for the item sold in 2012 is limited like this : 0,9 < S12 < 1. Is it possible to create this kind of limits ? (and if the answer is yes, how ?)

Thanks for your help

Regards

Arkhos94