private void lowestSellPrice(){ 
        if (Requests.isEmpty()) {
              highBuy = 0;
        }       
        
        float lowest;
        lowest = meanSellPrice;
        
        for (Request RequestX : Requests) {
            if (RequestX instanceof SellRequest) {
                if (lowest < RequestX.getUnitPrice()) {
                    lowest = RequestX.getUnitPrice();
                }
            }
        }                  
        lowSell = lowest;
    }