I have this model: $\left\{\begin{matrix} \textrm{max}[(0.2(1.07)^{-1}+0.2(1.07)^{-2}+0.9(1.07)^{-3})x_{A}+(0.4(1.07)^{-1}+0.5(1.07)^{-2}+0.3(1.07)^{-3})x_{B}]\\ 0.2x_{A}+0.4x_{B}\geq300.000 \\ 0.2x_{A}+0.5x_{B}\geq400.000\\x_{A}+x_{B}=1.000.000 \\x_{A},x_{B}\geq0 \end{matrix}\right.$
I have to find $x_{A}$ and $x_{B}$ with Excel. I'm inexperienced: how do I set up the program to use the iterative calculus? Thanks in advance for any help!