Hello everybody! Id like some help,i dont know how to calculate the total prize and the total items sold.There are 10 prizes and 10 items to be calculated.


<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0" xmlnssl="http://www.w3.org/1999/XSL/Transform">

<xsl:template match="/">
<html>
<body>
<h2>Furniture</h2>
<table border="1">
<tr bgcolor="#9acd32">
<th>Name</th>
<th>Address</th>
<th>Telephone number</th>
<th>Ordered_item</th>
<th>Start</th>
<th>Prize</th>
</tr>
<xsl:for-each select="Customers/Customer">
<tr>
<td><xsl:value-of select="Name"/></td>
<td><xsl:value-of select="Address"/></td>
<td><xsl:value-of select="Telephone_number"/></td>
<td><xsl:value-of select="Ordered_item"/></td>
<td><xsl:value-of select="start"/></td>
<td><xsl:value-of select="prize"/></td>
</tr>
</xsl:for-each>

</table>
</body>
</html>
</xsl:template>
</xsl:stylesheet>

I used that format:
<P>
<xsl:value-of select="//prize[1]"/>
<xsl:text> + </xsl:text>
<xsl:value-of select="//prize[2]"/>
<xsl:text> = </xsl:text>
<xsl:value-of select="//prize[1] + //prize[2]"/>
</P>

till "//prize[10]" but it only displays : 400+=NaN

The XML file:
<?xml version="1.0" encoding="ISO-8859-1"?>
<Customers>
<Customer>
<Name>John </Name>
<Address>19 Holloway Road </Address>
<Telephone_number>07827384928 </Telephone_number>
<Ordered_item>Sofa </Ordered_item>
<start>2012-02-20</start>
<prize>400</prize>
</Customer>

<Customer>
<Name>Nick</Name>
<Address>30 Holloway Road </Address>
<Telephone_number>09382930492 </Telephone_number>
<Ordered_item>Table</Ordered_item>
<start>2012-03-10</start>
<prize>200</prize>
</Customer>

<Customer>
<Name>Roger</Name>
<Address>13 Holloway Road </Address>
<Telephone_number>07823049828 </Telephone_number>
<Ordered_item>Bedside Cabinet </Ordered_item>
<start>2012-01-14</start>
<prize>100</prize>
</Customer>

<Customer>
<Name>Duncan</Name>
<Address>92 Holloway Road </Address>
<Telephone_number>07839482712</Telephone_number>
<Ordered_item>Sofa </Ordered_item>
<start>2012-04-23</start>
<prize>450</prize>
</Customer>

<Customer>
<Name>Chris </Name>
<Address>123 Holloway Road </Address>
<Telephone_number>072839402912 </Telephone_number>
<Ordered_item>Mattresses </Ordered_item>
<start>2012-02-22</start>
<prize>120</prize>
</Customer>

<Customer>
<Name>Matt</Name>
<Address>87 Holloway Road </Address>
<Telephone_number>072839402945 </Telephone_number>
<Ordered_item>Table </Ordered_item>
<start>2012-03-07</start>
<prize>98</prize>
</Customer>

<Customer>
<Name>Jake </Name>
<Address>72 Holloway Road </Address>
<Telephone_number>07263849271 </Telephone_number>
<Ordered_item>Bedside Cabinets </Ordered_item>
<start>2012-03-02</start>
<prize>25</prize>
</Customer>

<Customer>
<Name>Amy </Name>
<Address>69 Holloway Road </Address>
<Telephone_number>07877306301 </Telephone_number>
<Ordered_item>Table </Ordered_item>
<start>2012-03-29</start>
<prize>95</prize>
</Customer>

<Customer>
<Name>Francesca</Name>
<Address>90 Holloway Road </Address>
<Telephone_number>0772732348 </Telephone_number>
<Ordered_item>Mattresses </Ordered_item>
<start>2012-01-09</start>
<prize>150</prize>
</Customer>

<Customer>
<Name>Ryann </Name>
<Address>174 Holloway Road </Address>
<Telephone_number>078290375019</Telephone_number>
<Ordered_item>Sofa </Ordered_item>
<start>2012-04-22</start>
<prize>700</prize>
</Customer>

</Customers>

Thank you in advance!