The average age of 3 friends is 23. If the 4th friend’s age is added; the average remains 23. What is the 4th friend’s age

The average age of 3 friends is 23. If the 4th friend’s age is added; the average remains 23. What is the 4th friend’s age
A: 21
B: 23
C: 25
D: None of these

Three friends’ total age