Mule DataWeave Group by And Sum - sum

Question

I am doing something rather simple and hope that I am just missing a simple statement, I am trying to do a group by and sum but can not seem to be able to make DataWeave complete the task for me. Any help would be much appreciated!
I have the following XML
<?xml version="1.0" encoding="UTF-8"?>
<getRecordsResponse xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<getRecordsResult>
<company>0a6979a72ba5020092d4a5a667da15ac</company>
<u_billed_amount>504</u_billed_amount>
</getRecordsResult>
<getRecordsResult>
<company>548839a72ba5020092d4a5a667da15e0</company>
<u_billed_amount>29.17</u_billed_amount>
</getRecordsResult>
<getRecordsResult>
<company>0a6979a72ba5020092d4a5a667da15ac</company>
<u_billed_amount>33.75</u_billed_amount>
</getRecordsResult>
And the Following in a dataWeave expression -
%dw 1.0
%output application/xml
%namespace ns0 http://www.service-now.com/u_incident_task
---
results: {(
payload.getRecordsResponse.*getRecordsResult groupBy $.company map {
amtToBill: ($.u_billed_amount)
}
)}
Which yields the desired grouping, however I need to Sum the amount billed.
<?xml version='1.0' encoding='UTF-8'?>
<results>
<amtToBill>
<u_billed_amount>29.17</u_billed_amount>
</amtToBill>
<amtToBill>
<u_billed_amount>504</u_billed_amount>
<u_billed_amount>33.75</u_billed_amount>
</amtToBill>
</results>
What I need is the following
<?xml version='1.0' encoding='UTF-8'?>
<results>
<amtToBill>
<u_billed_amount>29.17</u_billed_amount>
</amtToBill>
<amtToBill>
<u_billed_amount>537.75</u_billed_amount>
</amtToBill>
</results>
I know there has to be a summation in dataWeave, I have not found it yet.

Answer 1

I found my own answer, just do this -
amtToBill: sum $.u_billed_amount