The Texas Consolidated Electronics Company is considering an R&D program encompassing eight research projects.

In the model for this problem $x_i$ is a $0-1$ variable for the selection of project $i,$ where $i=1$ to $8.$

One of the conditions in the model for this problem is project $2$ or project $5$ may be selected but both cannot be selected. That is$,$ one of the projects can be selected or neither of them can be selected.

This condition is represented by the following constraint:

$x_2{x}_5$

$x_2+x_{5}1$

$x_2{x}_5$

$x_2+x_5=1$