public IActionResult Index(Quotation quote)
 {
     if (ModelState.IsValid)
     {
         ViewBag.DiscountPercent = quote.CalcDiscountPercent();
         ViewBag.Discount        = quote.CalculateDiscount();
         ViewBag.Total           = quote.CalculateTotal();
         ViewBag.Sale            = quote.CalcSale();
     }
     else
     {
         ViewBag.Discount        = 0;
         ViewBag.Total           = 0;
         ViewBag.DiscountPercent = 0;
         ViewBag.Sale            = 0;
     }
     return(View(quote));
 }