Thirty five percent of all students who write exam clears. Twenty students were selected from a pool of students who wrote exam.
a. Assuming x as the number in 20 students who will clear the exam, write the formula for finding the probability

b. Use the formula to compute the probability that

1. exactly nine students clear the exam

ii. at least five students clear the exam

iii. three or fewer students clear the exam iv. at most two students clear the exam

v. at most 18 students clear the exam