In a student body election, 5% of the eligible voters are aged 18–21 years, 12% are aged 21–25 years, and the rest are older than 25 years. Among these groups, 80% of the 18– 21 year age group and 60% of the 21–25 year age group actually voted. If the number of voters aged 21–25 years who voted exceeds those aged 18–21 years by 320, what is the difference between the number of eligible voters aged 18–21 years and those aged 21– 25 years?