private void highestBuyPrice(){
        if (Requests.isEmpty()) {
              highBuy = 0;
        }       
        
        float highest;
        highest = meanBuyPrice;
        
        for (Request RequestX : Requests) {
            if (RequestX instanceof BuyRequest) {
                if (highest < RequestX.getUnitPrice()) {
                    highest = RequestX.getUnitPrice();
                }
            }
        }        
        highBuy = highest;
    }