Determining the couple moment (Mro)x,(Mro)y,(Mro)z and the solution manual is stating that i need to

Determining the couple moment (Mro)x,(Mro)y,(Mro)z and the solution manual is stating that i need to do vector r(ob) cross Fb + vector r(oc) cross Fd which doesnt make sense to me, shouldn’t it be vector r(ob) cross Fb + vector r(od) cross Fd? the answers don’t match up and so I need to know why the solution manual says to do it that way, that way doesn’t make sense.