A university found that 30% of its students withdraw without completing the introductory statistics course. Assume that 20 students registered for the course. If you compute the binomial probabilities manually, make sure to carry at least four decimal digits in your calculations.

1. Compute the probability that 2 or fewer will withdraw (to 4 decimals).
2. Compute the probability that exactly 4 will withdraw (to 4 decimals).
3. Compute the probability that more than 3 will withdraw (to 4 decimals).
4. Compute the expected number of withdrawals.