Simplify the following text for a Grade 5 native English-speaking person.
Original: Gluck 's masterly IphigÃ nie en Tauride was first produced on May 18 , 1779 .
Simplified: Then both composers were asked to write operas about the story IphigÃ nie en Tauride . Gluckâ s opera was first produced on 18 May 1779 .