how to sum the values from an XML file based on certain criteria

i need to sum up the values from an XML file based on some criteria

my XMl Is as follows

    <?xml version="1.0" encoding="utf-8" ?>
<transactions>
  <transcation ID="1">
    <BankName>ABC</BankName>
    <TemplatModel>CT1</TemplatModel>
    <Date>12/12/2014</Date>
    <Payeename>xyz</Payeename>
    <Amount>200</Amount>
  </transcation>
  <transcation ID="2">
    <BankName>EFG</BankName>
    <TemplatModel>CT2</TemplatModel>
    <Date>12/12/2014</Date>
    <Payeename>xyz</Payeename>
    <Amount>100</Amount>
  </transcation>
  <transcation ID="3">
    <BankName>ABC</BankName>
    <TemplatModel>CT1</TemplatModel>
    <Date>10/12/2014</Date>
    <Payeename>pqr</Payeename>
    <Amount>400</Amount>
  </transcation>
  <transcation ID="4">
    <BankName>EFG</BankName>
    <TemplatModel>CT2</TemplatModel>
    <Date>11/12/2014</Date>
    <Payeename>asd</Payeename>
    <Amount>300</Amount>
  </transcation>
</transactions>

i need to find the sum of amount where BankName="ABC"

and in another query i need to find the sum of amount whose date less than="12/12/2014"

and one more doubt which xml structure is better

      <transactions>
    <transcation ID="1" BankName="ABC" TemplatModel ="CT1" Date="12/12/2014" Payeename="asd" Amount="200"/>
    <transcation ID="2" BankName="EFG" TemplatModel ="CT2" Date="12/12/2014" Payeename="xyz" Amount="100"/>
    <transcation ID="3" BankName="ABC" TemplatModel ="CT1" Date="10/12/2014" Payeename="pqr" Amount="400"/>
    <transcation ID="4" BankName="EFG" TemplatModel ="CT2" Date="11/12/2014" Payeename="asd" Amount="300"/>
  </transactions>