function cal_mortgage(mf){
  var m_loan = mf.m_loan.value;
  m_loan=m_loan.replace(/[$\,\%\+]/g,'');
  var m_rate = mf.m_rate.value;
  m_rate=m_rate.replace(/[$\,\%\+]/g,'');
  var m_year = mf.m_year.value;
  m_year=m_year.replace(/[$\,\%\+]/g,'');

  var oneyear   = 12;
  var 利息 = m_rate / (oneyear * 100);
  var periods  = m_year * oneyear;
  var periodpayment = ( m_loan * ( 利息 / ( 1 - Math.pow( (1 + 利息) , (0 - periods) ) ) ) );
  periods = 0 - ( Math.log( 1 - (利息 * m_loan / periodpayment) ) / Math.log(1 + 利息) );
  var 利息_total = (periodpayment * periods) - m_loan;
	document.getElementById('mortgagesummary').innerHTML="<table widtd=100% style='width:100%;font-size:12px;color:#ff0000;line-height:16px;font-family: arial; font-weight:bold;background:#eeeeee;text-align:left;'><tr align=center><td colspan=2>还款信息:</td></tr><tr align=right><td>每月还款:</td><td>&nbsp;&nbsp;$"+Math.round(periodpayment*100)/100+"</td><tr><tr align=right><td>利息总计:</td><td>&nbsp;&nbsp;$"+Math.round(利息_total*100)/100+"</td></tr></table>";
}