public static CashRegister GetCashRegisterWithLeastNumberOfCustomers(this Customer customer, List <CashRegister> cashRegistersList)
        {
            var min = Int32.MaxValue;
            var tempCashRegister = new CashRegister(0);

            foreach (var cr in cashRegistersList)
            {
                if (cr.CustomersQueue.Count < min)
                {
                    min = cr.CustomersQueue.Count;
                    tempCashRegister = cr;
                }
            }

            return(tempCashRegister);
        }
        public static CashRegister GetCashRegisterWithLeastNumOfItems(this Customer customer, List <CashRegister> cashRegistersList)
        {
            var min = Int32.MaxValue;
            var allItemsOfCashRegister = 0;
            var tempCashRegister       = new CashRegister(0);

            foreach (var cr in cashRegistersList)
            {
                allItemsOfCashRegister = 0;
                foreach (var cs in cr.CustomersQueue)
                {
                    allItemsOfCashRegister += cs.NumberOfItemsInCart;
                }
                if (allItemsOfCashRegister < min)
                {
                    min = allItemsOfCashRegister;
                    tempCashRegister = cr;
                }
            }

            return(tempCashRegister);
        }