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HTML / CSS / JS

<?xml version="1.0" encoding="UTF-8"?>

<xsl:stylesheet version="1.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:output method="xml" indent="yes" encoding="UTF-8"/>

<xsl:template match="@*|node()">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()"/>
        </xsl:copy>
    </xsl:template>

<xsl:template match="price">
        <price>
            <xsl:copy-of select="@*"/>
            <xsl:value-of select="format-number(. * 1.1, '0.00')"/>
        </price>
    </xsl:template>

<xsl:template match="book">
        <xsl:copy>
            <xsl:apply-templates select="@*"/>
            <xsl:attribute name="priceIncreased">true</xsl:attribute>
            <xsl:apply-templates select="node()"/>
        </xsl:copy>
    </xsl:template>

<xsl:template match="book" mode="index">
        <xsl:value-of select="position()"/>
        <xsl:text>. </xsl:text>
        <xsl:value-of select="title"/>
        <xsl:text>&#10;</xsl:text>
    </xsl:template>

</xsl:stylesheet>