Simplify the following text for a Grade 6 native English-speaking person.
Original: ChÃ cents teau-Gontier is a commune in the Mayenne department in north-western France .
Simplified: ChÃ cents teau-Gontier is a commune of 11 131 people ( 1999 ) . It is found in the region Pays de la Loire in the Mayenne department in the northwest of France .