To cut costs while maintaining the quality of education, one of the board members of a school district proposed to have the number of teachers vary directly as the number of students in a classroom. She proposed 12 teachers to teach a student body of 228 students. How many teachers would be needed if the school grows to 399 students?
A. 19 teachers
B. 21 teachers
C. 20 teachers
D. 20.9 teachers