About 60% of U.S. full-time college students drank alcohol within a one-month period. You randomly select six U.S. full-time college students. Find the probability that the number of U.S. full-time college students who drank alcohol within a one-month period is 

(a) Exactly two, 

(b) At least three, and 

(c) Less than four.

Find the indicated probabilities using the geometric distribution, the Poisson distribution, or the binomial distribution. Then determine whether the events are unusual. If convenient, use a table or technology to find the probabilities.