How do I figure out median age of mothers from study when I am only given age ranges. See below: Mothers' age range (in years) with 25 participants

4 aged 20-30

16 aged 31-40

5 aged 41-50

Median for marital status

20 married, 1 divorced, 4 widowed

Median for educational background

12 have below high school diploma

5 have university degrees

8 have high school diploma

Median for occupation

22 are housewives, 3 employed