public Behaviour jobFor(Actor actor) {
    final Repairs b = Repairs.getNextRepairFor(actor, Plan.CASUAL) ;
    if (b != null) {
      final float priority = b.priorityFor(actor) ;
      if (priority * Planet.dayValue(world) >= Plan.ROUTINE) {
        return b ;
      }
    }
    if ((! structure.intact()) || (! personnel.onShift(actor))) return null ;
    final Choice choice = new Choice(actor) ;
    if (b != null) choice.add(b) ;
    
    final Service services[] = services() ;
    final Delivery d = Deliveries.nextCollectionFor(
      actor, this, services, 10, null, world
    ) ;
    choice.add(d) ;
    
    return choice.pickMostUrgent() ;
  }