max of sum

Hello friends,

Is there a way to get the max for a bunch of sum on an attribute.
I have the following XML and would like to find what's the highest expenses
(sum of all expense/@value). Which would be 303 .
any idea ?

<company>
   <department id="IT">
      <expense value="10"/>
      <expense value="12"/>
      <expense value="13"/>
      <expense value="18"/>
      <expense value="28"/>
   </department>

   <department id="Research">
      <expense value="40"/>
      <expense value="150"/>
      <expense value="75"/>
      <expense value="17"/>
      <expense value="21"/>
   </department>

   <department id="Finance">
      <expense value="34"/>
      <expense value="77"/>
   </department>

   <department id="HR">
      <expense value="22"/>
   </department>
</company>



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