The one way fare per person will be €29 if you book now on the Deutche Bahn website. Stopovers (which can be up to 48 hours) needs to be specified when booking. Routes you might consider are: Passau-Munich-Augsburg-Mainz-Koblenz-Trier-Luxembourg Passau-Wuerzburg-Mainz-Koblenz-Trier-...