The average age of 20 students of a class is 9 years. If 10 new students are admitted, the average age of the class is increased by 6 months. Find the average age of newly admitted students?

• A. 10 years 6 months
• B. 10 years 3 months
• C. 9 years 6 months
• D. 9 years 9 months
• E. None of these