Looking at arriving at Gare de Montparnasse at 11:37, then connecting to a train at Gare De Lyon. Departure time at Gare de Lyon dependent on how much time, conservatively, to get to Gare De Lyon and locate platform.
First time to Paris, so want to build in extra time to navigate Gare De Lyon.
Taxi travel time is 8 minutes, and public transportation goes up from there.
FYI, May 28 travel from Amboise (St-Pierre des Corps) to Paris, then to Antibes.
Thanks,
RS