Simplify the following text for a Grade 10 native English-speaking person.
Original: As emperor , Domitian strengthened the economy by revaluing the Roman coinage , expanded the border defenses of the empire , and initiated a massive building program to restore the damaged city of Rome .
Simplified: As emperor , Domitian strengthened the economy by revaluing the Roman coinage . He expanded the border defenses of the empire , and started a massive building program to restore the damaged city of Rome .