In a sample of college students, 50 percent are third year students and 70 percent are not second-year students. What fraction of those students who are not third-year students are second-year students? Pick one.
A) 2 / 3
B) 1 / 4
C) 2 / 5
D) 3 / 7
E) 2 / 9

Rationale: required answer = 40 / 60 . = 2 / 3 answer is a
Answer: A