Write SQL query to solve given problem: Calculate the average age of employee in each department and state which department has the youngest employees.. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT STRFTIME('%Y', CURRENT_TIMESTAMP) - STRFTIME('%Y', T1.BirthDate) + 1 , T3.Name FROM Employee AS T1 INNER JOIN EmployeeDepartmentHistory AS T2 USING (BusinessEntityID) INNER JOIN Department AS T3 USING (DepartmentID) ORDER BY T1.BirthDate DESC LIMIT 1