More Examples:

1. Find age of the youngest sailor with age >=18, for each rating with at least 2 such sailors and with every sailor under 60.
2. Find age of the youngest sailor with age>= 18, for each rating with at least 2 sailors between 18 and 60.
3. For each red boat, find the number of reservations for this boat
4. Find age of the youngest sailor with age > 18, for each rating with at least 2 sailors (of any age)
5. Find those ratings for which the average age is the minimum over all ratings