Ron, Age 19, Is a Full-Time Graduate Student at City

Ron, age 19, is a full-time graduate student at City University. During 2017, he received the following payments: ​
Ron served as a resident adviser in a dormitory and, therefore, the university waived the $2,500 charge for the room he occupied. What is Ron's adjusted gross income for 2017?

A) $1,500.
B) $3,900.
C) $9,000.
D) $15,400.
E) None of these.