XPATH 具有特定元素的最后一个元素

XPATH last element that have specific element

鉴于此 DTD：

<!ELEMENT root (t*)>
<!ELEMENT t (pay|gift)?>
<!ELEMENT pay EMPTY>
<!ATTLIST pay amount CDATA #IMPLIED >
<!ELEMENT gift (#PCDATA)>
<!ATTLIST gift amount CDATA #REQUIRED >

如何通过XPATH查询到上次赠送金额？

我会使用：

(//gift)[last()]/@amount