Best metro line and station to get into the centre of Paris driving in from Ivry La Bataille

The closest train station and train line from Ivry La Bataille into Paris would be from Dreux to Gare Montparnasse in Paris on the Transilien N-line train taking 1h10m in total (no transfers required, ride to end of the line, runs once per hour departing on the 52nd minute of each hour).
 
Dreux is a 25 minute drive south of Ivry-la-Bataille.