Quiz Teori SP

using System;

namespace Belajar
{
    class Quiz_Teori_SP
    {
        static void Main(string[] args)
        {
            string bangunRuang, caraBayar;
            int pilihMenu, jari2, tinggi, pilBR, x, y, z, nominalBeli, nominalPajak, total;
            double rumusVolume, a, pajak=0;

            Console.Title = "Menu Program Pilihan";
            Console.WriteLine(new string(' ', 16) + "PILUHAN");
            Console.WriteLine(new string('*', 40));
            Console.WriteLine("1. Bangun Ruang");
            Console.WriteLine("2. Fungsi");
            Console.WriteLine("3. Pembayaran");
            Console.WriteLine("4. Keluar");
            Console.WriteLine(new string('*', 40));
            Console.Write("Masukkan Pilihan [1/2/3/4] : ");
            pilihMenu = int.Parse(Console.ReadLine());

            if (pilihMenu == 1)
            {
                Console.Clear();
                Console.Write("Masukkan jari-jari   : ");
                jari2 = int.Parse(Console.ReadLine());
                Console.Write("Masukkan tinggi      : ");
                tinggi = int.Parse(Console.ReadLine());
                Console.WriteLine(new string('-', 40));
                Console.WriteLine(new string(' ', 10) + "Pilihan Bangun Ruang");
                Console.WriteLine(new string('-', 40));
                Console.WriteLine("1. Tabung");
                Console.WriteLine("2. Kerucut");
                Console.WriteLine(new string('-', 40));
                Console.Write("Masukkan Pilihan [1/2] : ");
                pilBR = int.Parse(Console.ReadLine());


                if (pilBR == 1)
                {
                    bangunRuang = "Tabung";
                    rumusVolume = 3.14 * jari2 * jari2 * tinggi;
                }
                else if (pilBR == 2)
                {
                    bangunRuang = "Kerucut";
                    rumusVolume = (double)1 / 3 * 3.14 * jari2 * jari2 * tinggi;
                }
                else
                {
                    bangunRuang = "";
                    rumusVolume = 0;
                }
                Console.WriteLine("\nVolume untuk " + bangunRuang + " dengan jari-jari " + jari2);
                Console.WriteLine("dan tinggi " + tinggi + " adalah " + rumusVolume);
            }
            else if (pilihMenu == 2)
            {
                Console.Clear();
                Console.Write("Masukkan nilai x : ");
                x = int.Parse(Console.ReadLine());
                Console.Write("Masukkan nilai y : ");
                y = int.Parse(Console.ReadLine());
                Console.Write("Masukkan nilai z : ");
                z = int.Parse(Console.ReadLine());
                Console.WriteLine(new string('-', 30));
                Console.WriteLine("a = 2x + 3y / 5z");
                Console.WriteLine(new string('-', 30));

                a = 2 * x + 3 * y / 5d * z;
                Console.WriteLine("Maka nilai a sebesar " + a.ToString("0,00"));
            }
            else if (pilihMenu == 3)
            {
                Console.Clear();
                Console.Write("Masukkan nominal beli : ");
                nominalBeli = int.Parse(Console.ReadLine());
                Console.Write("Masukkan cara bayar [Cash/Kredit] : ");
                caraBayar = Console.ReadLine();
                Console.WriteLine(new string('+', 40));

                if (caraBayar.ToLower() == "cash")
                {
                    pajak = 0.05;
                }
                else if (caraBayar.ToLower() == "kredit")
                {
                    pajak = 0.1;
                }
                else
                {
                    pajak = 0;
                    nominalBeli = 0;
                }
                nominalPajak = (int) (nominalBeli * pajak);
                total = nominalBeli + nominalPajak;

                Console.WriteLine("Nominal Pajak    : " + nominalPajak);
                Console.WriteLine("Total Bayar      : " + total);
            }
            else
            {
                Environment.Exit(0);
            }
            Console.ReadKey();
        }
    }
}