PHP Calculator

[webxaoz]

Здравейте, приятели искам да попитам как мога да направя това.
Цената да се калкулира според избраните бройки. И като се натисне бутона резултата да се записва в текстов файл не в база данни.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
</head>

<body>

<table width="373" height="103" border="1">
<tr>
<td width="123" height="29"> Model: № </td>
<td width="70"> Size: </td>
<td width="67">Produkti:</td>
<td width="85">Kraina Cena:</td>
</tr>

<tr>
<td height="26">
<select size="1" name="model" id="gender">
<option value="0025">0025</option>
<option value="0032">0032</option>
<option value="0045">0045</option>
<option value="0056">0056</option>
<option value="0063">0063</option>
</select>
</td>

<br />

<td>
<select size="1" name="size" id="gender">
<option value="m">M</option>
<option value="l">L</option>
<option value="xl">XL</option>
<option value="xxl">XXL</option>
</select>
</td>

<td>
<select size="1" name="colichestvo" id="gender">
<option value="1">1</option>
<option value="2">2</option>
<option value="5">5</option>
<option value="20">20</option>
</select>
</td>

<tr>
<td width="123" height="34">
<p><input type="submit" alt="SUBMIT" name="Submit" value="Izprati poruchkata" class="submit-text" /></p></td>

</tr>
</table>

<br />

Pezultat:<br />
-----------------------<br />
Produkti 5 <br />
Ha Stoinost: 18.50 lv<br />
Dostavka: 5.00 lv<br />
-----------------------<br />
Obshto: 23.50 lv

</body>
</html>