HarryPotter.ShoppingCartCalculator.CalculateDiscount C# (CSharp) Method

        private decimal CalculateDiscount(List<Book> bookList)
        {
            switch (bookList.Count)
            {
                case 2:
                    return bookList.Sum(book => book.Cost)*0.95M;
                case 3:
                    return bookList.Sum(book => book.Cost)*0.90M;
                case 4:
                    return bookList.Sum(book => book.Cost)*0.80M;
                case 5:
                    return bookList.Sum(book => book.Cost)*0.75M;
                default:
                    return bookList.Sum(book => book.Cost);
            }
        }