private void button2_Click(object sender, EventArgs e)
        {
            Double mpg;
            Double lkm;
            mpg = 2.352145833 * Double.Parse(textBox2.Text);
            lkm = (100 * 3.785411784) / (1.609344 * Double.Parse(textBox2.Text));

            if (checkBox3.Checked)
            {

                label5.Text = Convert.ToString(lkm);

            }
            if (checkBox4.Checked)
            {
                label5.Text = Convert.ToString(mpg);
            }