Groovy scripting

I want to perform some calculation of several values in a response and want to validate the outcome
of the calculation with other fields from the response using groovy script

For example
I want to sum up all the values of hours*norm that are found in the response

SUM =
(Record1/Data/Data1/hours*norm) + (Record1/Data/Data2/hours*norm) +
(Record2/Data/Data1/hours*norm) + (Record2/Data/Data2/hours*norm)

The SUM will be compared with another value in the response, with Value of Buget/TotalAmount

Can anyone help me out with this?

XML:

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
   <s:Body xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
      <Resultaat xmlns="http://tempuri.org/">
         <Records>
            <Record1>
               <Record1A>
                  <StartDate xmlns="">2015-01-01</StartDate>
                  <EndDate xmlns="">2016-03-21</EndDate>
                  <ID xmlns="">257404491</ID>
                  <Budget xmlns="">
                     <TotalAmount>3521397</TotalAmount>
                     <StartDate>2015-01-01</StartDate>
                     <EndDate>2015-12-31</EndDate>
                     <MaxAmount>52820</MaxAmount>
                     <Functiebudget>
                        <Bedrag>3521397</Bedrag>
                     </Functiebudget>
                  </Budget>
                  <Budget xmlns="">
                     <TotalAmount>788392</TotalAmount>
                     <StartDate>2016-01-01</StartDate>
                     <EndDate>2016-03-21</EndDate>
                     <MaxAmount>0</MaxAmount>
                     <Functiebudget>
                        <Bedrag>788392</Bedrag>
                     </Functiebudget>
                  </Budget>
               </Record1A>
               <Data>
                  <Data1>
                     <ID>3749908</ID>
                     <Hours>173685</Hours>
                     <NORM>0.01</NORM>
                     <DTStartDate>2015-01-01T00:00:00</DTStartDate>
                     <DTEndDate>2016-03-21T00:00:00</DTEndDate>
                  </Data1>
                  <Data2>
                     <ID>3749908</ID>
                     <Hours>173685</Hours>
                     <NORM>0.01</NORM>
                     <DTStartDate>2015-01-01T00:00:00</DTStartDate>
                     <DTEndDate>2016-03-21T00:00:00</DTEndDate>
                  </Data2>
               </Data>
            </Record1>
            <Record2>
               <Record2A>
                  <StartDate xmlns="">2015-01-01</StartDate>
                  <EndDate xmlns="">2016-03-21</EndDate>
                  <ID xmlns="">257404491</ID>
                  <Budget xmlns="">
                     <TotalAmount>3521397</TotalAmount>
                     <StartDate>2015-01-01</StartDate>
                     <EndDate>2015-12-31</EndDate>
                     <MaxAmount>52820</MaxAmount>
                  </Budget>
                  <Budget xmlns="">
                     <TotalAmount>788392</TotalAmount>
                     <StartDate>2016-01-01</StartDate>
                     <EndDate>2016-03-21</EndDate>
                     <MaxAmount>0</MaxAmount>
                  </Budget>
               </Record2A>
               <Data>
                  <Data1>
                     <ID>3749908</ID>
                     <Hours>173685</Hours>
                     <NORM>0.01</NORM>
                     <DTStartDate>2015-01-01T00:00:00</DTStartDate>
                     <DTEndDate>2016-03-21T00:00:00</DTEndDate>
                  </Data1>
                  <Data2>
                     <ID>3749908</ID>
                     <Hours>173685</Hours>
                     <NORM>0.01</NORM>
                     <DTStartDate>2015-01-01T00:00:00</DTStartDate>
                     <DTEndDate>2016-03-21T00:00:00</DTEndDate>
                  </Data2>
               </Data>
            </Record2>
         </Beschikkingen>
      </Resultaat>
   </s:Body>
</s:Envelope>