Help for a real newbie

I am trying to get the final result of my calculations to have comma's in the numerical answer. Also Why am I getting a neg number as my answer? Take a look if you wouldn't mind and let me know if you have any ideas.
All js and html below:
<!-- CALCULATOR -->
<html>
<title>MCF Calculator</title>

<script language="JavaScript">

function CalculateSum(Atext, Btext, Ctext, Dtext, Etext, Ftext, form)
{
var A = parseFloat(Atext);
var B = parseFloat(Btext);
var C = parseFloat(Ctext);
var D = parseFloat(Dtext);
var E = parseFloat(Etext);
var F = parseFloat(Ftext);

form.Answer.value= Math.round((A * 30 * B)* (C/100 -1)* (D/100 -1) * (E/100 -1) + F);

}

function ClearForm(form)
{
form.input_A.value = "";
form.input_B.value = "";
form.input_C.value = "";
form.input_D.value = "";
form.input_E.value = "";
form.input_F.value = "";

}

</script>

<body text="white" bgcolor="#990000" background="">

<p><center><font size="+2"> MCF Calculator</font></center>
<center>
<hr style="WIDTH: 100%; HEIGHT: 11px" width="100%" color="#008000" size="11"></center><font size="5">
<center>
<table height="320" width="956" align="left" border="0">

<tr><!-- Row 1 -->
<td>
<div align="center">

<form name="Calculator" method="post">
<p align="left">******
Total Daily Production**<input style="HEIGHT: 25px" size="4" name="input_A">*<font size="1">(All
Wells)<br><br></font>*********************Price
Per*Unit* <input style="HEIGHT: 25px" size="4" name="input_B">*<font size="1">(MCF)<br><br></font>**********
State
Severance Tax* <input style="HEIGHT: 25px" size="4" name="input_C">*%<font size="1"><br></font><br>****************************
** *LORI** <input style="HEIGHT: 25px" size="4" name="input_D">*% <font size="1">(Land Owner
Royalty)<br></font><br>******************************
* ORRI** <input style="HEIGHT: 25px" size="4" name="input_E">*% <font size="1">(Overwrite
Royalty)<br><br></font>***************
Field Expenses*<font size="4"><strong>\$ </strong></font>
<input style="HEIGHT: 25px" size="4" name="input_F">*<font size="1">(Monthly Supervision and
Maintainence)<br><br><br><br>**************************************************
<input style="WIDTH: 189px; HEIGHT: 28px" onclick="CalculateSum(this.form.input_A.value, this.form.input_B.value, this.form.input_C.value, this.form.input_D.value, this.form.input_E.value, this.form.input_F.value, this.form)"type="button" size="34" value="Click Here to Calculate" name="AddButton"><br></font><br>**************
Net Profit * =* <input size="9" name="Answer" style="WIDTH: 108px; HEIGHT: 25px">*(Per Month)<br><br><br><br>****************************************
*<input type="button" value="Reset" name="ClearButton" onclick="ClearForm(this.form)" style="WIDTH: 102px; HEIGHT: 28px" size="16"></p>
</form></div><br></td><!-- Col 1 --></tr></table></center>

</body>
</html>