HELP! The XSLT may be easy, but I could not figure it

Can anyone help? Thanks in advance.

I have the xml document like:

<response>
  <all>
    <data>12345A</data>
    <data>22345B</data>
    <data>32345A</data>
    <data>42345B</data>
    <data>52345B</data>
    <data>62345A</data>
    <data>72345A</data>
  <all>
</response>

And like to transform it to another xml document. For all <data> under the
<all>, Start a new group
with the <group> following with <amount> when the last character of context
of the <data> is A; otherwise add the <amount> with the context when
the last character of the context of the <data> is "B".

I had tried with for-each and following, but could not get what I want.

<response>
  <group>
    <amount>12345A</amount>
    <amount>22345B</amount>
  </group>
  <group>
    <amount>32345A</amount>
    <amount>42345B</amount>
    <amount>52345B</amount>
  </group>
  <group>
    <amount>62345A</amount>
    <amount>72345B</amount>
  </group>
</response>

Have a nice day!

Piming Kuo