protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void widthTextBox_TextChanged(object sender, EventArgs e)
        {
            if (!EntryError()) return;

        }

        double width = 0;
        double length = 0;
        double height = 0;


        private bool EntryError()

        {
            if (!double.TryParse(widthTextBox.Text.Trim(), out width)) return false;
            if (!double.TryParse(heightTextBox.Text.Trim(), out height)) return false;
            if (!double.TryParse(lengthTextBox.Text.Trim(), out length)) length = 1;

            double volume = width * height * length;
            calculateTheCost(volume);

            return true;


        }

        private void calculateTheCost(double volume)


        {
            double postageMultipler = getPostageMultiplier() * volume;

            displayResult(postageMultipler);

        }

        private double getPostageMultiplier()
        {
            if (groundRadioButton.Checked) return .15;
            if (airRadioButton.Checked) return .25;
            if (nextDayRadioButton.Checked) return .45;
            else return 0;
        }

        private void displayResult(double postageMultipler)
        {
           resultLabel.Text = string.Format("Your parcel will cost {0:C} to ship", postageMultipler.ToString());

        }
    }