Muenchian Grouping and Sum

Hiya folks. I'm learning the ropes of XSLT 1.0 using MSXSL v1.0.0.1and
I'm having a real hard time with the following problem. Given the XML:

<ItemList>
<Item>
<PLU>1234678</PLU>
<Qnt>4</Qnt>
<Price>17.49</Price>
</Item>
<Item>
<PLU>1234670</PLU>
<Qnt>5</Qnt>
<Price>17.49</Price>
</Item>
<Item>
<PLU>1234678</PLU>
<Qnt>2</Qnt>
<Price>17.49</Price>
</Item>
</ItemList>

I'm trying to group these items by PLU using Muenchian grouping, which
I know how to do, but I'm also supposed to sum the Qnt and the Price,
which is where I fail. Could someone show me how it's done? Thanks.

-Bret