The average age of a family having three members is 40 years. The smallest member of the family is 18 years old. The difference between the age of the oldest family member and the age of the second oldest family member is 6 more than the difference between the age of the second oldest member and age of youngest member of the family.

Quantity I: 25 years hence, what will be the average of the age of smallest member and that of oldest member of the family?

Quantity II: What is the age of the oldest member of the family?