private void Calculate_Click(object sender, EventArgs e)
{
  int insurance_type = Convert.ToInt32(textBox3.Text);
  int salary = Convert.ToInt32(textBox4.Text);
  double insurance, tax, pay;
  insurance = 0.0;
  switch (insurance_type)
  {
    case 1:
        insurance = (double)salary * 7 / 100;
        break;
    case 2:
        insurance = (double)salary * 9 / 100;
        break;
    case 3:
        insurance = (double)salary * 10 / 100;
        break;
   }
   tax = salary * 0.1;
   pay = salary - tax - insurance;
   label5.Text = "Insurance is  " + insurance.ToString();
   label6.Text = "Tax is    " + tax.ToString();
   label7.Text = "Pay is   " + pay.ToString();			
}
