According to the college registrar's office at University A, 40% of students enrolled in STATS 100 this semester are freshmen, 30% are sophomores, 20% are juniors and 10% are seniors. There are...

Exact probability statistics

Extracted text: According to the college registrar's office at University A, 40% of students enrolled in STATS 100 this semester are freshmen, 30% are sophomores, 20% are juniors and 10% are seniors. There are thousands of students taking the course. 5 students are randomly selected from rosters of STATS 100. a) What's the probability that exactly 2 of them are seniors? b) What's the probability that at least 4 of them are sophomores?