$As$ 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 $8is$ selected

unless project $3is$ selected.

For integer programming problems, which one $of$ the alternatives listed

below correctly models this situation?

$x3+x6+x81$

$x8x3,x6x3$

$x3x8,x3x6$

$x6x8,x3x8$