Simplify the following text for a Grade 10 native English-speaking person.
Original: Ã `` scar Rafael de JesÃ s Arias SÃ nchez ( born 13 September 1940 ) is a Costa Rican politician who was President of Costa Rica from 2006 to 2010 .
Simplified: Oscar Arias , born on 13 September 1940 in the city of Heredia , is a former President of Costa Rica .