✅ how to set the outputs to do all the math

namespace Uber
{

    public partial class Form1 : Form
    {
        double[,] uberfares = { { 2.50, 0.18, 0.81, 2.75 }, { 5.00, 0.35, 1.55, 3.00 }, { 5.00, 0.35, 1.80, 3.60 } };

        int selectedbutton = 0;

        public Form1()
        {
            InitializeComponent();
        }

        private void button4_Click(object sender, EventArgs e)
        {
            basefareoutput.Text = selectedbutton.ToString();


        }

        private void Form1_Load(object sender, EventArgs e)
        {
            int pickup;
            int destantion;
            int distance;
            int traveltime;
            int basefare;
            int permin;
            int perkm;
            int bookingfee;
            int totalfare;

        }

        private void textBox9_TextChanged(object sender, EventArgs e)
        {
            //   int sub = (2.50) + (quantityMin * 0.18) + (quantityBookinfee * 2.75); 



        }
        // this changes colours of buttons when clicked and other buttons colours
        private void uberxbutton_click(object sender, EventArgs e)
        {

            uberxbutton.BackColor = SystemColors.ControlDark;

            uberxlbutton.BackColor = SystemColors.Control;

            uberselectbutton.BackColor = SystemColors.Control;

            selectedbutton = 1;

        }

        private void uberxlbutton_Click(object sender, EventArgs e)
        {
            uberxlbutton.BackColor = SystemColors.ControlDark;

            uberxbutton.BackColor = SystemColors.Control;

            uberselectbutton.BackColor = SystemColors.Control;
            selectedbutton = 2;
        }

        private void uberselectbutton_Click(object sender, EventArgs e)
        {
            uberselectbutton.BackColor = SystemColors.ControlDark;

            uberxlbutton.BackColor = SystemColors.Control;

            uberxbutton.BackColor = SystemColors.Control;
            selectedbutton = 3;

        }
    }
}