A college biology class consists of 8% freshmen, 27% sophomores, 45 % juniors and 20% seniors. During an exam, 22% of the freshmen, 17% of the sophomores, 12 % of the juniors, and 5% of the seniors wrote their answers in pen. If you would select an exam at random and find that the answers were written in pen, what is the probability that the exam was written by a freshmen?