The average marks obtained by a group of 25 students was 29. One student left the group as a result of which the average of the remaining students rose to 29.5. Afterwards, another student came in as a result of which the average marks of the group dropped to 28.8. What is the average of the combined marks obtained by the student who left and the one who joined?

A

14

B

14.5

C

15

D

13.5