public static void Main()
Console.WriteLine("enter book_price");
book_price=double.Parse(Console.ReadLine());
Console.WriteLine("enter n_book");
n_book=int.Parse(Console.ReadLine());
total_price=book_price*n_book;
Console.WriteLine("the total price is {0} ",total_price);
Console.WriteLine("enter d_price");
d_price=total_price*3.45;
Console.WriteLine("the d_price is {0}",d_price);