public string Start()
        {
            _console.Write("Enter Product with Unit Price \n Ex : Product1 UnitPrice \n keep Blank to end");

            string[] inputs = _console.ReadTillBreak();

            List <Product> products = FetchProducts(inputs);

            _console.Write("Enter Rules  \n Ex : 3 of A's for 130 OR C & D for 30 \n keep Blank to end");
            inputs = _console.ReadTillBreak();

            List <IRule> rules = FetchRules(products, inputs);

            products = ProductQuantitySet(products);

            CalculateProductPrices(products);
            ApplyPromotionToProducts(rules);

            return(CalculateTotal(products));
        }