Form 1

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace HOA6
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Button1_Click(object sender, EventArgs e)
        {
            string output = "";

            Form2 f2 = new Form2();

            Hide();

            f2.ShowDialog();

            Show();

            if (checkBox1.Checked)
            {
                Class1.finalbill = Class1.totalbill * .9;

                output += "Gen Ad\t\t" + "x" + Class1.genad + "\t Php " + Class1.genadtotal + "\r\nLower Box\t" + "x" + Class1.lowerbox + "\t Php " + Class1.lowerboxtotal + "\r\nPatron\t\t" + "x" + Class1.patron + "\t Php " + Class1.patrontotal + "\r\nTotal Bill: Php" + Class1.totalbill + "\r\nSchool Discount: 10% \r\n" + "Final Bill: Php " + Class1.finalbill ;
            }
            else
            {
                Class1.finalbill = Class1.totalbill;

                output += "Gen Ad\t\t" + "x" + Class1.genad + "\t Php " + Class1.genadtotal + "\r\nLower Box\t" + "x" + Class1.lowerbox + "\t Php " + Class1.lowerboxtotal + "\r\nPatron\t\t" + "x" + Class1.patron + "\t Php " + Class1.patrontotal + "\r\nTotal Bill: Php" + Class1.totalbill + "\r\nNo Discount Selected\r\n" + "Final Bill: Php " + Class1.finalbill;


            }



            textBox1.Text = output;


        }
    }
}