Advanced XPath query support

Hi,

I am quite new to Drupal and XPath. I need to import some data from the following xml file:

<?xml version="1.0"?>
<order id="invoice 1">    
    <detail>
	<type>apple</type>
        <quantity>10</quantity>
        <price>20</price>
    </detail>
    <detail>
	<type>banana</type>
        <quantity>5</quantity>
        <price>3</price>
    </detail>
</order>

I am using the following mapping:

Context: //order
title: @id
field_type: detail/type
field_quantity: detail/quantity
field_price: detail/price
field_full_price: detail/quantity * detail/price

I am getting the following output:

invoice 1

type:
apple
banana
quantity:
10
5
price:
20.00
3.00
full price:
200.00

My 1st problem is, that I dont get the full price of the second product.
My 2nd problem is, that I dont know if its possible to get an output formatted like this:

type:..........quantity:..........price:..........full price:
apple...............10...............20...............200
banana...............5...............3...............15

(like a table or similar look)

My 3rd problem is, that I would need a field, which would represent the sum of full prices (in this case, it should be 215), but I dont know how the XPath query should look.

I would really appreciate any help. Thank you !