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 that if project $2$ is selected, project $5$ must also be selected $($but not vice versa $-$ i$.$e$.,$ if project $5$ is selected, project $2$ does not have to be selected$).$

This condition is represented by the following constraint: