function a_times_b(form) {
a=eval(form.a.value)
b=eval(form.b.value)
c=(a*b)*.0125
if(c<40){
  c=40
}
if(form.isIowa.checked==true){
 c=c+(c*.06);
}
form.ans.value=formatCurrency(c);
}
function formatCurrency(num) {
  num = num.toString().replace(/\$|\,/g,'');
  if(isNaN(num))
    num = "0";
  sign = (num == (num = Math.abs(num)));
  num = Math.floor(num*100+0.50000000001);
  cents = num%100;
  num = Math.floor(num/100).toString();
  if(cents<10)
     cents = "0" + cents;
  for (var i = 0; i < Math.floor((num.length-(1+i))/3); i++)
     num = num.substring(0,num.length-(4*i+3))+','+
           num.substring(num.length-(4*i+3));
  return (((sign)?'':'-') + '$' + num + '.' + cents);
}