decimal CalculateTotalPromoted(Receipt receipt, Promotion[] promotions)
{
string[] barcodes =
promotions.Where(p => p.Type == "BUY_ONE_HUNDRED_CUT_FIFTY")
.Select(p => p.BarCode)
.ToArray();
decimal totalAfterPromoted = receipt.ReceiptItems.Where(r => barcodes.Contains(r.Product.Barcode))
.Select(r => (r.Total - r.Promoted)).Sum();
return (int)(totalAfterPromoted/100)*50;
}
