Example 18 : 10 years ago the average age of all the 25 teachers of the girls college was 45 years. 4 years ago the principal has retired from her post at the a

Example 18 : 10 years ago the average age of all the 25 teachers of the Girls college was 45 years. 4 years ago the principal has retired from her post at the age of 60 year. So after one year a new principal whose age was 54 years recruited from outside. The present average age of all the teachers is, if principal is also considered as a teacher 18 (A) 5425 years (B) 5525 years (C) 49 years (D) None of these