public void tryToFill(){
    if (!l.hasNext()) return; // if there is no line
    
    for(int i=0;i<pumps.size();i++){
      if (pumps.get(i).free()&&freeAttendant()){
        Car c = l.next();
        pumps.get(i).fill(c);
        pumps.get(i).askAttendant(attendants);
        if (c.getWaitTime()>19) late++;
        System.out.println(carCount+","+c.getWaitTime()+"");
        grossProfit += profitEarned(c);
        carCount ++;
        return;
      }
      
    }
    return;
  }