SELECT DISTINCT T1.age FROM management AS T2 JOIN head AS T1 ON T1.head_id  =  T2.head_id WHERE T2.temporary_acting  =  'Yes'
What are the distinct ages of the heads who are acting?
[Schema (values) (types)]: | department_management |  department : department_id (text) , name (number) , creation (text) , ranking (text) , budget_in_billions (number) , num_employees (number) | head : head_id (text) , name (number) , born_state (text) , age (text) | management : department_id (text) , head_id (number) , temporary_acting (text);