As a project manager, Mary is managing $12$ different projects. She realized

something very interesting related to them. Sometimes they present some

unique and particular rules, like the ones for projects #:$3,6,$ and $8.$ She

concluded that neither project $6$ nor project $8$ is selected unless project $3$ is

selected.

For integer programming problems, which one of the alternatives listed

below correctly models this situation?

$x3+x6+x81$

$x8x3,x6x3$

$x3x8,x3x6$

$x6x8,x3x8$