GUI Problem in Java Program

Hello experts! I'm working on this good 'ole mortgage calculator program, and trust me...I've looked for solutions and I've stared at my code for days and compared, but I cannot get the radio button row to appear below the principle input box instead of across the top. Simple, I'm sure. But I'm stumpled. Now I know this program has other issues/problems going on before it does what it's meant to do, but for now I want to get the GUI set up. Could you please take a look and see what I'm doing wrong? Thank you in advance!

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.*;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.Locale;

import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.border.Border;
import javax.swing.border.EmptyBorder;

public class MortgageCalculator extends JFrame implements ActionListener
{
    double rate = 0;  //APR
    double monthlyPayment = 0; //Monthly payment amount
    double principle = 0; //Amount of loan
    int term = 0; //Mortgage term in years
    double interest = 0; //Interest, in months
    int notePeriod = 0; //Mortgage term in months

    String mTerm[] = {"7", "15", "30"};
    String mRate[] = {"5.35%", "5.50%", "5.75%"};

    //Labels and Input Fields

    JPanel row1 = new JPanel();
    JLabel mortgageLabel = new JLabel("MORTGAGE CALCULATOR", JLabel.CENTER);

    JPanel row2 = new JPanel(new GridLayout(1, 2));
    JLabel principleLabel = new JLabel("Mortgage Principle $",JLabel.LEFT);
    JTextField principleTxt = new JTextField(8);

    JPanel radioPanel = new JPanel();
    JRadioButton buttonA = new JRadioButton("7 Years at 5.35%" , false);
    JRadioButton buttonB = new JRadioButton("15 Years at 5.50%" , false);
    JRadioButton buttonC = new JRadioButton("30 Years at 5.75%", false);

    JPanel row5 = new JPanel(new GridLayout(1, 2));
    JLabel monthlyPaymentLabel = new JLabel("Monthly Payment $", JLabel.LEFT);
    JTextField monthlyPaymentTxt = new JTextField(8);

    //Create buttons
    JPanel button = new JPanel(new FlowLayout(FlowLayout.CENTER, 8, 8));
    JButton amortizeButton = new JButton("Amortize Payments");
    JButton clearButton = new JButton("Clear");
    JButton exitButton = new JButton("Exit");
    JButton calculateButton = new JButton("Calculate");

    JTextArea displayArea = new JTextArea(10, 30);
    JScrollPane scroll = new JScrollPane(displayArea);

    public MortgageCalculator()
    {
        super ("Mortgage Payment Calculator"); //Header
        setSize(450, 400); //GUI frame size
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            Container pane = getContentPane();

        Border rowborder = new EmptyBorder( 3, 10, 3, 10 ); //Border around elements inside frame

        //Pane and row properties, GUI layout
        JPanel panel = new JPanel(new GridLayout(4,1));
        panel.add(row1);
        row1.add(mortgageLabel);
        row1.setMaximumSize( new Dimension( 1000, row1.getMinimumSize().height));
        row1.setBorder( rowborder);

        panel.add(row2);
        row2.add(principleLabel);
        row2.add(principleTxt);
        row2.setMaximumSize( new Dimension( 1000, row2.getMinimumSize().height));
        row2.setBorder( rowborder);

        ButtonGroup bgroup = new ButtonGroup();
        bgroup.add(buttonA);
        bgroup.add(buttonB);
        bgroup.add(buttonC);

        radioPanel.setLayout(new FlowLayout(FlowLayout.RIGHT, 4, 4 ));
        radioPanel.add(buttonA);
        radioPanel.add(buttonB);
        radioPanel.add(buttonC);

        pane.add(radioPanel);
        radioPanel.setMaximumSize( new Dimension( 10000, radioPanel.getMinimumSize().height));
        radioPanel.setBorder( rowborder);

        panel.add(row5);
        row5.add(monthlyPaymentLabel);
        row5.add(monthlyPaymentTxt);
        monthlyPaymentTxt.setEnabled(false); //Set payment amount uneditable
        row5.setMaximumSize( new Dimension( 1000, row5.getMinimumSize().height));
        row5.setBorder( rowborder);

        panel.add(button); //Add buttons
        button.add(calculateButton);
        button.add(clearButton);
        button.add(exitButton);
        button.add(amortizeButton);
        pane.add(panel);
        button.setMaximumSize( new Dimension( 1000, button.getMinimumSize().height));

       scroll.setBorder(BorderFactory.createEmptyBorder(10,10,10,10));
        pane.add(scroll);

        pane.setLayout(new BoxLayout( pane, BoxLayout.Y_AXIS));
        setVisible(true);
        setContentPane(pane);

        amortizeButton.addActionListener(this); //Add listeners
        clearButton.addActionListener(this);
        exitButton.addActionListener(this);
        calculateButton.addActionListener(this);
        buttonA.addActionListener(this);
        buttonB.addActionListener(this);
        buttonC.addActionListener(this);

    }

    public void actionPerformed(ActionEvent event)
    {
        Object command = event.getSource();

           if(command == calculateButton)
      {
          try
          {
              principle = Double.parseDouble(principleTxt.getText());
          }
      catch(NumberFormatException e)
      {
          //Select rate and term
          if(buttonA.isSelected() == true)
          {
              rate = 5.35;
              term = 7;
          }
          else if(buttonB.isSelected() == true)
          {
              rate = 5.5;
              term = 15;
          }
          else if (buttonC.isSelected() == true)
          {
              rate = 5.75;
              term = 30;
          }
          else //none of the buttons  are selected,  this is an actual error.  Throw an exception
          {
              JOptionPane.showMessageDialog(null, "Invaild Entry!  Please Try Again", "ERROR", JOptionPane.ERROR_MESSAGE);
          }
                     }

      //Calculate monthly interest rate
      interest = ((rate / 100) / 12);

      //Calculate total number of payments
      notePeriod = term * 12; // (for example, 5 years means notePeriod = 60)

       //Calculate monthly payment
      if (rate == 0.0)
      {
          monthlyPayment = principle / notePeriod;
      }
      else
          {
              monthlyPayment = (principle * interest) / (1 - Math.pow(1 + interest, -notePeriod));
          }

      //Currency formatter
      NumberFormat myCurrencyFormatter;
      myCurrencyFormatter = NumberFormat.getCurrencyInstance(Locale.US);
      monthlyPaymentTxt.setText(myCurrencyFormatter.format(monthlyPayment));
        }

        if(command == clearButton)
        {
             principleTxt.setText(null);
             monthlyPaymentTxt.setText(null);
             displayArea.setText(null);
        }

        if(command == exitButton)
        {
             System.exit(0);
        }
        if (command == amortizeButton)
        {
      double year = 0;
      double interest = 0;
      double balance = 0;
      double monthlyInterest = 0;
      int x = 1;
      int months = term * 12;
      String titles = "Month\t Principle\tInterest\tBalance\n";

      interest = (rate / 100) /12;
      balance = principle;

      displayArea.setText(titles);

      for (x = 1; x <= months; ++x)
      {
          //Calculate Detailed Payment Info
          monthlyInterest = balance * interest;

          if(interest != 0)

          year = monthlyPayment - monthlyInterest;
          balance = principle - year;

          //Format Variables
          DecimalFormat df = new DecimalFormat("\u00A4#,##0.00"); //Crrency
          DecimalFormat pf = new DecimalFormat("#,##0.00%"); //Percentages
          DecimalFormat mi = new DecimalFormat("#,##0.000%"); //Percentages

          //Positions the Cursor to the Top of the TextArea
          displayArea.setCaretPosition(0);
          displayArea.append((months +1) + ")\t"+df.format(principle)+"\t"+df.format(interest)+"\t"+df.format(balance)+"\n");
      }
            }
    }

    public void Payment()
    {
    //Get user input
    principle = Double.parseDouble(principleTxt.getText());

    //Calculate monthly interest rate
    interest = ((rate / 100) / 12);

    //Calculate total number of payments
    notePeriod = term * 12;

    //Calculate monthly payment
    if (rate == 0.0)
    {
        monthlyPayment = principle / notePeriod;
    }
    else
        {
            monthlyPayment = (principle * interest) / (1 - Math.pow(1 + interest, -notePeriod));
        }

    //Currency formatter
    NumberFormat myCurrencyFormatter;
    myCurrencyFormatter = NumberFormat.getCurrencyInstance(Locale.US);
    monthlyPaymentTxt.setText(myCurrencyFormatter.format(monthlyPayment));
}
    public static void main (String[] arguments) //Main Method
    {
        MortgageCalculator smc = new MortgageCalculator();
        smc.setVisible(true);
        smc.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
 } //End of program